Two-fluid spray burner

ABSTRACT

An object of the present invention is to provide a two-fluid spray burner in which liquid fuel can be stably supplied without causing large fluctuation in flow rate of supplied liquid fuel even when the flow rate of supplied liquid fuel is low. In a two-fluid spray burner ( 11 ) which atomizes liquid fuel ( 24 ) with atomizing air and burns the same, the burner includes: a liquid fuel tank ( 19 ) including a cylindrical side portion ( 20 ) and a bottom portion ( 21 ) provided at a lower end of the side portion ( 20 ), the liquid fuel tank ( 19 ) storing liquid fuel ( 24 ) supplied from a liquid fuel supply tube ( 25 ) and discharging the stored liquid fuel ( 24 ) from a liquid fuel discharge hole ( 22 ) opened in the bottom portion ( 21 ) below a liquid level ( 23 ) of the stored liquid fuel ( 24 ). The liquid fuel ( 24 ) discharged from the liquid fuel discharge hole ( 22 ) of the liquid fuel tank ( 19 ) is atomized with atomizing gas ( 46 ) and is burned.

TECHNICAL FIELD

The present invention relates to a two-fluid spray burner which burns liquid fuel atomized with atomizing gas.

BACKGROUND ART

A two-fluid spray burner burns liquid fuel atomized with atomizing gas and is used as a heat source of a reformer of a fuel power generation system or the like, for example.

In a conventional two-fluid spray burner, liquid fuel is supplied from a pump of a liquid fuel supply system through a liquid fuel supply tube and discharged from an end of the liquid fuel supply tube. The liquid fuel discharged from the liquid fuel supply tube is mixed with atomizing air, so that the liquid fuel is atomized and burned.

Patent Document 1: Japanese Patent Laid-open No. 2002-224592

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, the above-described conventional two-fluid spray burner is designed on assumption that the liquid fuel is supplied from the pump at a high flow rate. Accordingly, when the conventional two-fluid spray burner is used in a state where flow of supplied liquid fuel is low, the liquid fuel is intermittently (in a vibrating manner) supplied from the pump, and the liquid fuel is therefore intermittently discharged from an end 1A of a liquid fuel supply tube 1 as illustrated in FIG. 14(a). Accordingly, as illustrated in FIG. 14( b), the flow rate of supplied liquid fuel greatly fluctuates. This prevents stable supply of liquid fuel and makes it difficult to achieve stable combustion, thus generating unburned exhaust gas or causing accidental fire.

One of the countermeasures to this problem is to increase pump performances of the liquid fuel supply system so that fuel is stably supplied even at a low flow rate. However, such a countermeasure requires an expensive pump and increases costs of the apparatus.

Accordingly, in the light of the aforementioned circumstances, an object of the present invention is to provide a two-fluid spray burner capable of stably supplying liquid fuel without causing large fluctuations in flow rate of supplied liquid fuel even when the flow rate of supplied liquid fuel is low.

Means for Solving the Problems

A two-fluid spray burner of a first invention to solve the aforementioned problems is a two-fluid spray burner which atomizes liquid fuel with atomizing gas and burns the atomized liquid fuel, characterized by comprising:

a liquid fuel tank including: a cylindrical side portion and a bottom portion provided at a lower end of the side portion, the liquid fuel tank storing liquid fuel supplied from a liquid fuel supply tube and discharging the stored liquid fuel from one or a plurality of liquid fuel discharge holes opened in the side or bottom portion at a position below a liquid level of the stored liquid fuel, the burner characterized in that

the liquid fuel discharged from the liquid fuel discharge hole of the liquid fuel tank is atomized with the atomizing gas and burned.

A two-fluid spray burner of a second invention is the two-fluid spray burner of the first invention characterized in that the liquid fuel discharge holes are opened in the bottom portion of the liquid fuel tank,

the burner characterized by further comprising:

a cylindrical atomizing gas passage formed between the side portion of the liquid fuel tank and an outer cylinder surrounding a periphery of the side portion; and

a two-fluid spray nozzle provided at a lower end portion of the outer cylinder and including a lower nozzle main body and an upper atomizing gas introduction portion, the two-fluid spray nozzle having:

-   -   a two-fluid converging space portion formed under the liquid         fuel discharge holes, in central part of the nozzle main body         and the atomizing gas introduction portion;     -   one or a plurality of spray holes formed in the nozzle main body         and leading to the two-fluid converging space portion; and     -   one or a plurality of grooves formed in the atomizing gas         introduction portion and allowing the two-fluid converging space         portion and the atomizing gas passage to communicate with each         other,

the burner characterized in that

the liquid fuel tank is installed on the atomizing gas introduction portion, and

the liquid fuel which is discharged from the liquid fuel discharge holes to flow into the two-fluid converging space portion converges at the two-fluid converging space portion with the atomizing gas which flows down the atomizing gas passage and flows through the grooves at the atomizing gas introduction portion to be introduced to the two-fluid converging space portion, and the liquid fuel is then sprayed together with the atomizing gas from the spray holes.

A two-fluid spray burner according to a third invention is the two-fluid spray burner of the second invention characterized in that

an undersurface of the bottom portion of the liquid fuel tank is formed as a tapered surface portion which is tapered,

a top surface of the atomizing gas introduction portion is also formed as a tapered surface portion which is tapered, and

the liquid fuel tank is installed on the atomizing gas introduction portion with the tapered surface portion of the liquid fuel tank abutted and fitted to the tapered surface portion of the atomizing gas introduction portion.

A two-fluid spray burner of a fourth invention is the two-fluid spray burner of the first invention characterized in that the liquid fuel discharge holes are opened in the bottom portion of the liquid fuel tank, the burner characterized by further comprising:

a cylindrical atomizing gas passage formed between the side portion of the liquid fuel tank and an outer cylinder surrounding a periphery of the side portion; and

a two-fluid spray nozzle provided at a lower end portion of the outer cylinder, the two-fluid spray nozzle having:

-   -   a two-fluid converging space portion formed in central part         under the liquid fuel discharge holes, and     -   one or a plurality of spray holes formed, leading to the         two-fluid converging space portion,

the burner characterized in that

the undersurface of the bottom portion of the liquid fuel tank is formed as a tapered surface portion which is tapered,

the top surface of the two-fluid spray nozzle is also formed as a tapered surface portion which is tapered,

the liquid fuel tank is installed on the two-fluid spray nozzle with the tapered surface portion of the liquid fuel tank abutted and fitted to the tapered surface portion of the two-fluid spray nozzle,

one or a plurality of grooves are formed at the bottom portion of the liquid fuel tank, the grooves allowing the atomizing gas passage and the two-fluid converging space portion to communicate with each other, and

the liquid fuel discharged from the liquid fuel discharge holes to flow into the two-fluid converging space portion converges at the two-fluid converging space portion with the atomizing gas which flows down the atomizing gas passage and then flows through the grooves at the bottom portion of the liquid fuel tank to be introduced to the two-fluid converging space portion, and the liquid fuel is then sprayed together with the atomizing gas from the spray holes.

A two-fluid spray burner of a fifth invention is the two-fluid spray burner of any one of the second to fourth inventions characterized in that

the two-fluid converging space portion has a circular shape in a top view, and

the grooves of the atomizing gas introduction portion or the grooves of the bottom portion of the liquid fuel tank are formed along tangent directions of a circumference of the two-fluid converging space portion in the top view.

A two-fluid spray burner of the sixth invention is the two-fluid spray burner according to any one of the second to fourth inventions, characterized in that the two-fluid converging space portion has a circular shape in a top view, and

the grooves of the atomizing gas introduction portion or the grooves of the bottom portion of the liquid fuel tank are formed along radial directions of the two-fluid converging space portion in the top view.

A two-fluid spray burner of a seventh invention is the two-fluid spray burner of the fifth or sixth invention characterized in that the plurality of grooves of the atomizing gas introduction portion or the plurality of grooves of the bottom portion of the liquid fuel tank are formed at positions rotationally symmetric around a central axis of the two-fluid converging space portion.

A two-fluid spray burner of an eighth invention is the two-fluid spray burner of any one of the second to seventh inventions, the burner characterized by further comprising:

a press member pressing the liquid fuel tank downward, in which

the bottom portion of the liquid fuel tank is pressed against the atomizing air introduction portion of the two-fluid spray nozzle to be brought into firm contact or

the bottom portion of the liquid fuel tank is pressed against the two-fluid spray nozzle to be brought into firm contact.

A two-fluid spray burner of a ninth invention is the two-fluid spray burner of the first invention, characterized in that

the liquid fuel discharge holes are opened in the bottom portion of the liquid fuel tank,

the burner characterized by further comprising:

a cylindrical first atomizing gas passage formed between the side portion of the liquid fuel tank and an outer cylinder surrounding a periphery of the side portion; and

a two-fluid spray nozzle provided at a lower end portion of the outer cylinder, the two-fluid spray nozzle having:

-   -   a two-fluid converging space portion formed in center part under         the liquid fuel discharge holes and     -   one or a plurality of spray holes formed, leading to the         two-fluid converging space portion,

the burner characterized in that

the top surface of the two-fluid spray nozzle is formed as a tapered surface portion which is tapered,

the undersurface of the bottom portion of the liquid fuel tank is formed as a tapered surface portion which is tapered,

a plurality of supporting portions protrude on the side portion of the liquid fuel tank, and each undersurface of the supporting portions is formed as a tapered surface portion,

the liquid fuel tank is installed on the two-fluid spray nozzle with the tapered surface portions of the supporting portions being abutted and fitted to the tapered surface portion of the two-fluid spray nozzle,

gap formed by the supporting portions between the tapered surface portion of the liquid fuel tank and the tapered surface portion of the two-fluid spray nozzle is a second atomizing gas passage, and

the liquid fuel discharged from the liquid fuel discharge holes to flow into the two-fluid converging space portion converges at the two-fluid converging space portion with the atomizing gas which flows down the first atomizing gas passage, passes through atomizing gas passage portions between the supporting portions, and flows through the second atomizing gas passage to be introduced to the two-fluid converging space portion and is then sprayed together with the atomizing gas from the spray holes.

A two-fluid spray burner of a tenth invention is the two-fluid spray burner of any one of the second to ninth inventions characterized in that the two-fluid converging space portion is a reverse conical shape, and the spray holes are formed at a vertex position of the reverse conical space.

A two-fluid spray burner of an eleventh invention is the two-fluid spray burner of any one of the second to tenth inventions, the burner characterized by further comprising a cylindrical gas fuel passage formed between the outer cylinder and a gas fuel supply tube surrounding a periphery of the outer cylinder,

the burner characterized in that gas fuel flows down the gas fuel passage and is sprayed from a lower end of the gas fuel passage to be burned.

A two-fluid spray burner of a twelfth invention is the two-fluid spray burner according to any one of the first to eleventh inventions, characterized in that an end of the liquid fuel supply tube is in contact with an inner peripheral surface of the side portion of the liquid fuel tank.

The two-fluid spray burner of any one of the first and second inventions may further include the following configurations.

The two-fluid spray burner of a first configuration is the two-fluid spray burner of any one of the first and second inventions, which sprays liquid fuel from the two-fluid spray nozzle of a two-fluid sprayer to the combustion space under the two-fluid spray nozzle and burns the same, the burner characterized by further comprising:

a cylindrical combustion air passage formed between the two-fluid sprayer and a burner outer cylinder surrounding a periphery of the two-fluid sprayer;

a shielding plate separating the combustion air passage and the combustion space; and

a combustion air hole provided on an outer periphery of the shielding plate, characterized in that

the combustion air which flows down the combustion air passage is blocked by the shielding plate, introduced to the outer periphery of the shielding plate to be kept away from the fuel spray nozzle, and flow through the combustion air hole into the combustion space.

The two-fluid spray burner of a second configuration is the two-fluid spray burner of the first configuration, characterized in that

a cylinder extending downward from a undersurface of the shielding plate for delaying supply of combustion air is provided to form different cylindrical combustion air passage between the cylinder and the burner outer cylinder, the different combustion air passage leading to the combustion air hole, and

after passing through the combustion air hole, the combustion air flows down the different combustion air passage and flows into the combustion space from a lower end of the different combustion air passage.

The two-fluid spray burner of a third configuration is the two-fluid spray burner of the second configuration, characterized in that

one or a plurality of cylinders extending downward from the undersurface of the shielding plate for preventing stagnation are provided within the cylinder for delaying supply of the combustion air.

The two-fluid spray burner of a fourth configuration is the two-fluid spray burner of any one of the first to third configuration, characterized in that

in the shielding plate, a plurality of other combustion air holes are formed in a position inside the combustion air hole.

EFFECT OF THE INVENTION

According to the two-fluid spray burner of the first invention, the two-fluid spray burner is provided with the liquid fuel tank which includes the cylindrical side portion and the bottom portion provided at the lower end of the side portion. The liquid fuel tank stores the liquid fuel supplied from the liquid fuel supply tube and discharges the stored liquid fuel from the liquid fuel discharge holes which are opened in the side or bottom portion thereof, below the liquid level of the stored liquid fuel. The liquid fuel discharged from the liquid fuel discharge holes of the liquid fuel tank is atomized with the atomizing gas and is burned. Accordingly, in the two-fluid spray burner thus configured, even when the liquid fuel is intermittently supplied from the liquid fuel supply tube to the liquid fuel tank, the liquid fuel stored in the liquid fuel tank is continuously discharged from the liquid fuel discharge holes of the liquid fuel tank. In other words, even when the supply flow rate of a pump of a liquid fuel supply system is low and the liquid fuel is intermittently supplied from the liquid fuel supply tube to the liquid fuel tank, the liquid level of the liquid fuel stored in the liquid fuel tank fluctuates a little up and down to cause the flow rate of the liquid fuel discharged from the liquid fuel discharge hole to fluctuate a little. The flow rate of supplied liquid fuel does not fluctuate much unlike the conventional one. The liquid fuel can be therefore stably supplied even when the flow rate of supplied liquid fuel is low, thus achieving stable combustion is facilitated and the possibility of producing unburned exhaust gas and causing accidental fire is eliminated.

According to the two-fluid spray burner of the second invention, the liquid fuel which is discharged from the liquid fuel discharge holes to flow into the two-fluid converging space portion converges with the atomizing gas which flows down the atomizing gas passage and passes through the grooves at the atomizing gas introduction portion to be introduced into the two-fluid converging space portion and is then sprayed together with the atomizing air from the spray holes. Accordingly, in the two-fluid spray burner thus configured, the liquid fuel is well mixed with the atomizing air whose flow speed is increased at the grooves (with the horizontal speed component increased), at the two-fluid converging space portion and is then sprayed from the spray holes of the two-fluid spray nozzle. Compared to the case of not providing the two-fluid converging space portion and grooves, therefore, the spread angle of the sprayed liquid fuel is larger, and the liquid fuel is surely atomized, thus improving the combustion characteristics.

According to the two-fluid spray burner of the third invention, the liquid fuel tank is installed on the atomizing gas introduction portion with the tapered surface portion of the liquid fuel tank abutted and fitted to the tapered surface portion of the atomizing gas introduction portion. It is therefore easy to align the central axes of the liquid fuel tank and two-fluid spray nozzle. Accordingly, the liquid fuel tank is installed at the center, and it is possible to equalize the width of the atomizing gas passage in the circumferential direction and equalize the flow of the atomizing gas in the atomizing gas passage in a circumferential direction. This makes it possible to secure symmetric properties of the liquid fuel sprayed from the spray hole of the two-fluid spray nozzle (or symmetric properties of the flame).

According to the two-fluid spray burner of the fourth invention, the liquid fuel discharged from the liquid fuel discharge hole to flow into the two-fluid converging space portion converges at the two-fluid converging space portion with the atomizing gas which flows down the atomizing gas passage and the flows through the grooves at the bottom portion of the fuel tank to be introduced to the two-fluid converging space portion and is then sprayed together with the atomizing gas through the spray holes. Accordingly, in the two-fluid spray burner thus configured, the liquid fuel is well mixed with the atomizing gas whose flow speed increased at the grooves (with the horizontal speed component increased), at the two-fluid converging space portion and then sprayed through the spray holes. Compared to the case of not providing the two-fluid converging space portion and grooves, therefore, the spread angle of the liquid fuel is larger, and the liquid fuel is surely atomized, thus improving the combustion characteristics.

Furthermore, the liquid fuel tank is installed on the two-fluid spray nozzle with the tapered surface portion of the liquid fuel tank being abutted and fitted to the tapered surface portion of the two-fluid spray nozzle. It is therefore easy to align the central axes of the liquid fuel tank and two-fluid spray nozzle. Accordingly, the liquid fuel tank is installed at the center, and it is possible to equalize the width of the atomizing gas passage in the circumferential direction and thus equalize the flow of the atomizing gas in the atomizing gas passage in the circumferential direction. It is therefore possible to secure the symmetric properties of the liquid fuel sprayed from the spray holes of the two-fluid spray nozzle (or symmetric properties of flame).

According to the two-fluid spray burner of the fifth invention, the grooves of the atomizing gas introduction portion or the grooves of the bottom portion of the liquid fuel tank are formed along tangent directions of the circumference of the two-fluid converging space portion in a top view. Accordingly, the atomizing gas is swirled and mixed with the liquid fuel at the two-fluid converging space portion, and the liquid fuel and atomizing gas are thus mixed more surely. The liquid fuel sprayed through the spray hole of the two-fluid spray nozzle can be therefore surely atomized, thus improving the combustion characteristics of the liquid fuel.

According to the two-fluid spray burner of the sixth invention, the grooves of the atomizing gas introduction portion or the grooves of the bottom portion of the liquid fuel tank are formed along the radial directions of the two-fluid converging space portion in a top view. The atomizing gas therefore collides with the liquid fuel at the two-fluid converging space portion to be mixed with the liquid fuel, and the liquid fuel and atomizing gas are more surely mixed. Accordingly, the liquid fuel sprayed from the spray holes of the two-fluid spray nozzle can be atomized more surely, thus further improving the combustion characteristics of the liquid fuel.

According to the two-fluid spray burner of the seventh invention, the plurality of grooves of the atomizing gas introduction portion or the plurality of grooves of the bottom portion of the liquid fuel tank are formed at positions rotationally symmetric around the central axis of the two-fluid converging space portion. Accordingly, the distribution of the liquid fuel sprayed from the spray holes of the two-fluid spray nozzle in the circumferential direction can be equalized, thus improving the combustion characteristics of the liquid fuel.

According to the two-fluid spray burner of the eighth invention, the two-fluid spray burner is provided with the press member pressing the liquid fuel tank downward. The bottom portion of the liquid fuel tank is thus pressed against the atomizing gas introduction portion of the two-fluid spray nozzle to be brought into firm contact, or the bottom portion of the liquid fuel tank is thus pressed against the two-fluid spray nozzle to be brought into firm contact. Accordingly, the undersurface of the bottom portion of the fuel tank and the top surface of the atomizing gas introduction portion are brought into firm contact. In other words the tapered surface portion of the liquid fuel tank and the tapered surface portion of the atomizing gas introduction portion or the tapered surface portion of the liquid fuel tank and the tapered surface portion of the two-fluid spray nozzle are brought into firm contact, thus preventing formation of gap between these contact surfaces. It is therefore possible to prevent the atomizing gas from flowing through portions other than the grooves and allow the effect of wide spraying by the grooves to be sufficiently exerted.

According to a two-fluid spray burner of the ninth invention, the liquid fuel discharged from the liquid fuel discharge holes to flow into the two-fluid converging space portion converges at the two-fluid converging space portion with the atomizing gas which flows down the first atomizing gas passage, passes through the atomizing gas passage portions between the supporting portions, and then flows through the second atomizing gas passage to be introduced to the two-fluid converging space portion and is then sprayed together with the atomizing gas from the spray holes. Accordingly, in the two-fluid spray burner thus configured, the liquid fuel is mixed with the atomizing gas at the two-fluid converging space portion and is then sprayed from the one of plurality of spray holes of the two-fluid spray nozzle. Compared to the case of not providing the two-fluid converging space portion, therefore, the spread angle of the sprayed liquid fuel is larger, and the liquid fuel is surely atomized, thus improving the combustion characteristics.

According to the two-fluid spray burner of the tenth invention, the two-fluid converging space portion is a reverse conical shape, and the spray holes are formed at the vertex position of the reverse conical space. Accordingly, the liquid fuel and atomizing gas can be more surely mixed at the two-fluid converging space portion. The liquid fuel sprayed from the spray holes is more surely atomized, thus further improving the combustion characteristics of the liquid fuel.

According to the two-fluid spray burner of the eleventh invention, the two-fluid spray burner includes a cylindrical gas fuel passage formed between the outer cylinder and the gas fuel supply tube surrounding a periphery of the outer cylinder. The gas fuel flows down the gas fuel passage and is then sprayed from the lower end of the gas fuel passage to be burned. Accordingly, in the two-fluid spray burner thus configured, the gas fuel sprayed from the cylindrical gas fuel passage is uniform in the circumferential direction. It is therefore possible to improve the combustion characteristics, thus exerting a flame holding effect by the gas fuel when the liquid fuel is supplied at a low flow rate, for example.

According to the two-fluid spray burner of the twelfth invention, the end portion of the liquid fuel supply tube is in contact with the inner peripheral surface of the side potion of the liquid fuel tank, so that the liquid fuel flows down the inner peripheral surface even when the flow rate of the liquid fuel discharged from the liquid fuel supply tube is low. It is therefore possible to further stabilize the discharge of the liquid fuel from the liquid fuel discharge hole. In other words, when the liquid fuel falls in droplets, the liquid level of the liquid fuel stored in the liquid fuel tank greatly fluctuates. In the case where the liquid level is very low, there might be a case where the liquid fuel discharge holes are temporarily exposed to stop the discharge of the liquid fuel. However, allowing the liquid fuel to flow down the inner peripheral surface of the liquid fuel tank can prevent occurrence of such a disadvantage.

According to the two-fluid spray burner of the first configuration, the combustion air flowing down the combustion air passage is blocked by the shielding plate and then introduced to the outer periphery of the shielding plate to be kept away from the fuel spray nozzle. The combustion air then passes through the combustion air hole and flows into the combustion space. Accordingly, only a part of the combustion air is mixed at the combustion space with the fuel sprayed from the fuel spray nozzle and used for combustion of the fuel. The residual combustion air further flows down and is mixed with combustion exhaust gas produced by the combustion. It is therefore possible to achieve proper mixture of the combustion air and fuel through one supply of the combustion air (with one step) and produce a large amount of combustion exhaust gas without exceedingly cooling flame. It is possible to achieve a burner such as a two-fluid spray burner which is capable of producing a large amount of combustion exhaust gas with a simple configuration and does not generate unburned gas and cause accidental fire.

Moreover, the combustion air is caused to flow into the combustion space at the position away from the fuel spray nozzle by the shielding plate. Accordingly, the position where a part of the combustion air is supplied to fuel can be set downward away from the shielding plate. The position of flame is also set downward away from the shielding plate, thus preventing adherence of soot to the undersurface of the shielding plate. A lot of soot sticking to the undersurface of the shielding plate may cause disadvantages such as clogging of the fuel spray nozzle due to the soot and abnormal heating of the fuel spray due to the soot absorbing radiation heat from flame. However, by preventing adherence of soot to the undersurface of the shielding plate as described above, such disadvantages can be prevented from occurring.

Moreover, according to the two-fluid spray burner of the second mode, the cylinder extending downward from the undersurface of the shielding plate for delaying supply of the combustion air is provided, and the additional cylindrical combustion air passage leading to the combustion air hole is formed between the cylinder and the burner outer cylinder. The combustion air which flows through the combustion air hole is thus allowed to flow down the different combustion air passage and then flow into the combustion space from the lower end of the combustion air passage. In this configuration, it is therefore possible to delay supply of a part of the combustion air to the fuel sprayed from the fuel spray nozzle. In other words, the position where a part of the combustion air is supplied to the fuel can be set downward away from the shielding plate. Accordingly, the position of flame is set downward away from the shielding plate, thus preventing adherence of soot to the undersurface of the shielding plate. The operational effect of setting the position where a part of the combustion air is supplied to the fuel downward away from the shielding plate can be also obtained by provision of only the shielding plate as described above. However, as described in the second invention, by providing the cylinder for delaying supply of the combustion air, the position where a part of the combustion air is supplied to the fuel can be more surely set downward away from the shielding plate.

In the aforementioned first configuration, when the shielding plate cannot be made so large because of restriction on size of the burner and the like and the distance between the fuel spray nozzle and combustion air hole cannot be made long enough, the amount of the part of the combustion air supplied to the fuel is too much, and the flame could be excessively cooled. On the contrary, by providing the cylinder for delaying supply of combustion air like the second configuration, the position where the part of the combustion air is supplied to the liquid fuel can be set downward away from the shielding plate, and the part of the combustion air supplied to the fuel can be reduced to a proper amount. Accordingly, provision of the cylinder like the second invention is effective in such a view. By providing the cylinder, the shielding plate can be reduced in size, and the burner can be miniaturized.

According to the two-fluid spray burner of the third configuration, one or plurality of the cylinders extending downward from the undersurface of the shielding plate for preventing stagnation are provided within the cylinder for delaying supply of combustion air. Accordingly, stagnation (convection) of the fuel can be prevented from occurring near the undersurface of the shielding plate by the cylinder for preventing stagnation. It is therefore possible to prevent the fuel stagnating near the undersurface of the shielding plate from catching fire and adhering of soot to the undersurface of the shielding plate.

According to the two-fluid spray burner of the fourth configuration, one or plurality of additional combustion air holes are formed in the shielding plate portion inside the one or plurality of combustion air holes, so that a part of the combustion air flows through these additional combustion air holes. Accordingly, such a flow of the combustion air can suppress stagnation of the combustion air occurring near the undersurface of the shielding plate, thus preventing adherence of soot to the shielding plate. Moreover, the cool combustion air flows near the fuel spray nozzle through the additional combustion air holes. It is therefore possible to obtain a cooling effect, with the combustion air, on the fuel spray nozzle which tends to be excessively heated by radiation heat from flame.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal sectional view showing a structure of a two-fluid spray burner according to Embodiment 1 of the present invention.

FIG. 2 is a transverse sectional view taken along a line A-A of FIG. 1.

FIG. 3 is a transverse sectional view taken along a line B-B of FIG. 1.

FIG. 4( a) is an enlarged longitudinal sectional view showing a two-fluid sprayer provided for the two-fluid spray burner of FIG. 1, and FIG. 4( b) is a transverse sectional view taken along a line C-C of FIG. 4( a).

FIG. 5( a) is an enlarged longitudinal sectional view showing lower part of the two-fluid sprayer, and FIG. 5( b) is a top view (a view in the direction of arrows D of FIG. 5 (a)) showing a two-fluid spray nozzle provided for the two-fluid sprayer.

FIG. 6( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 2 of the present invention, and FIG. 6( b) is a top view (a view in the direction of arrows E of FIG. 6( a)) showing a two-fluid spray nozzle provided for the two-fluid sprayer.

FIG. 7( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 3 of the present invention, and FIG. 7( b) is a top view (a view in the direction of arrows F of FIG. 7( a)) showing a two-fluid spray nozzle provided for the two-fluid sprayer.

FIG. 8( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 4 of the present invention (a longitudinal section view taken along the G-G line of FIG. 8( b)); FIG. 8( b) is a bottom view (a view in the direction of an arrow H of FIG. 8( a)) showing a liquid fuel tank provided for the two-fluid sprayer; FIG. 8( c) is a view in the direction of an arrow I of FIG. 8( b); and FIG. 8( d) is a transverse sectional view taken along a line J-J of FIG. 8( a).

FIG. 9( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 5 of the present invention (a cross-sectional view taken along a line K-K of FIG. 9( b)); FIG. 9( b) is a bottom view (a view in the direction of an arrow L of FIG. 9( a)) showing a liquid fuel tank provided for the two-fluid sprayer; and FIG. 9( c) is a transverse sectional view taken along a line M-M of FIG. 9( a).

FIG. 10( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 6 of the present invention. FIG. 10( b) is a transverse sectional view taken along a line L-L of FIG. 10( b).

FIG. 11 is a longitudinal sectional view showing configuration of a two-fluid spray burner according to Embodiment 7 of the present invention.

FIG. 12 is a transverse sectional view taken along a line M-M of FIG. 11.

FIG. 13 is a system diagram schematically showing a fuel cell power generation system according to Embodiment 8 of the present invention.

FIG. 14( a) is a view showing liquid fuel intermittently discharged from an end of a liquid fuel supply tube in a conventional two-fluid spray burner, and FIG. 14( b) is a view showing great fluctuations in flow rate of supplied liquid fuel in the conventional two-fluid spray burner.

EXPLANATION OF REFERENCE NUMERALS

11, TWO-FLUID SPRAY BURNER; 12, TWO-FLUID SPRAYER; 13, COMBUSTION SPACE; 14, GAS FUEL PASSAGE; 15, COMBUSTION AIR PASSAGE; 16, FIRST CYLINDER; 17, SECOND CYLINDER; 18, PLATE; 19, LIQUID FUEL TANK; 20, SIDE PORTION, 20 a, INNER PERIPHERAL SURFACE; 20 b, OUTER PERIPHERAL SURFACE; 21, BOTTOM PORTION; 21 a, INNER SURFACE (TOP SURFACE); 21 b, OUTER SURFACE (UNDERSURFACE); 21 b-1, OUTSIDE PORTION; 21 b-2, INSIDE PORTION; 22, LIQUID FUEL DISCHARGE HOLE; 23, LIQUID LEVEL; 24, LIQUID FUEL; 24A, CONTOUR; 25, LIQUID FUEL SUPPLY TUBE; 25A, END PORTION (BOTTOM END); 26, WASHER; 27, SPRAYER OUTER CYLINDER; 27A, LOWER END PORTION; 27B, UPPER END PORTION; 28, ATOMIZING AIR PASSAGE; 29, AIR INLET HOLE; 30, ATOMIZING AIR SUPPLY TUBE; 30A, END PORTION; 31, CAP; 32, 33, THREAD PORTION; 31A, LOWER PORTION; 31B, STEP PORTION; 34, O-RING; 35, WASHER; 36, COIL SPRING; 37, ATOMIZING GAS INTRODUCTION PORTION; 37 a, TOP SURFACE; 37 b, INNER PERIPHERAL SURFACE; 38, TWO-FLUID SPRAY NOZZLE; 38 a, INNER SURFACE (TOP SURFACE); 39, NOZZLE BODY; 40, GROOVE; 41, SPACE; 42 SPACE (RECESS); 43, TWO-FLUID CONVERGING SPACE PORTION; 44, SPRAY HOLE; 45, GAP; 46, ATOMIZING AIR; 47, GAS FUEL SUPPLY TUBE; 48, BURNER OUTER CYLINDER; 48 a, INNER PERIPHERAL SURFACE; 49, GAS FUEL; 50, COMBUSTION AIR; 51, PROTRUSION; 52, COMBUSTION AIR PASSAGE HOLE; 53, COMBUSTION AIR PASSAGE; 54, SPARK PLUG; 61, GROOVE; 81, GROOVE; 91, SUPPORT PORTION; 91 a, UNDERSURFACE; 91 a-1, OUTSIDE PORTION; 92, ATOMIZING AIR PASSAGE; 93, ATOMIZING AIR PASSAGE PORTION; 101, COMBUSTION AIR PASSAGE HOLE; 111, REFORMER; 112, COMBUSTION FURNACE; 113 FUEL CELL

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, a description is given of embodiments of the present invention with reference to the drawings.

Embodiment 1

FIG. 1 is a longitudinal sectional view showing a configuration of a two-fluid spray burner according to Embodiment 1 of the present invention. FIG. 2 is a transverse sectional view taken along a line A-A of FIG. 1. FIG. 3 is a transverse sectional view taken along a line B-B of FIG. 1. FIG. 4( a) is an enlarged longitudinal sectional view showing a two-fluid sprayer provided in the two-fluid spray burner of FIG. 1, and FIG. 4( b) is a transverse sectional view taken along a line C-C of FIG. 4( a). FIG. 5( a) is an enlarged longitudinal sectional view showing lower part of the two-fluid sprayer, and FIG. 5( b) is a top view (a view in the direction of arrows D) showing a two-fluid spray nozzle provided for the two-fluid sprayer.

Based on FIGS. 1 to 3, a schematic description is given of a two-fluid spray burner 11 of Embodiment 1. The two-fluid spray burner 11 includes a burner outer cylinder 48. Within the burner outer cylinder 48, a two-fluid sprayer 12 is placed in upper central part, and a combustion space 13 is under the two-fluid sprayer 12. A gas fuel supply passage 14 is formed around the two-fluid sprayer 12, and around the gas fuel supply passage 14, a combustion air supply passage 15 is formed. The combustion air supply passage 15 and combustion space 13 are partitioned with a plate 18 as a shielding plate. On an undersurface of the plate 18, a first cylinder 16 as a cylinder for delaying supply of combustion air and a second cylinder 17 as a cylinder for preventing stagnation are provided.

Based on FIGS. 4 and 5, a description is given of a configuration of the two-fluid sprayer 12 in detail. Note that, the two-fluid sprayer 12 sprays two fluids which are liquid fuel and atomizing gas (atomizing air), in other words, atomizes the liquid fuel with atomizing gas and sprays the same.

As shown in FIGS. 4 and 5, the two-fluid sprayer 12 has a liquid fuel tank 19 built-in. The liquid fuel tank 19 has a structure including a cylindrical side portion (a body portion) 20 and a bottom portion 21 provided at a bottom end of the side portion 20. Within the liquid fuel tank 19, liquid fuel 24 for burner combustion is stored, and a fine liquid fuel discharge hole 22 is opened at the center of the bottom portion 21 of the liquid fuel tank 19. The liquid fuel discharge hole 22 is positioned below a liquid level 23 of the liquid fuel 24 stored in the liquid fuel tank 19.

Specifically, the liquid fuel 24 supplied from a liquid fuel supply tube 25 is once stored in the liquid fuel tank 19. The stored liquid fuel 24 is discharged from the liquid fuel tank 19 through the liquid fuel discharge hole 22 at the bottom. At this time, height of the liquid level 23 of the liquid fuel 24 stored in the liquid fuel tank 19 (height from an inner surface 21 a of the bottom portion 21 to the liquid level 23) is a height which provides a liquid column head (described in detail later) corresponding to a pressure loss of the liquid fuel 24 flowing through the liquid fuel discharge hole 22. Examples of the liquid fuel 24 for burner combustion can be kerosene, heavy oil, alcohol, ether and the like.

In the liquid fuel supply tube 25, an end portion (a lower end portion) 25A is inserted downward from an upper end of the liquid fuel tank 19 into the liquid fuel tank 19 and is provided to be positioned in central part of the liquid fuel tank 19 above the liquid level 23. The base end of the liquid fuel supply tube 25 is connected to a liquid fuel supply pump of an unillustrated liquid fuel supply system.

As indicated by a dashed-dotted line in FIG. 5( a), the end portion 25A of the liquid fuel supply tube 25 may be in contact with an inner peripheral surface 20 a of the side portion 20 of the liquid fuel tank 19. When the liquid fuel 24 is supplied at a low flow rate, the liquid fuel 24 drops in droplets as illustrated in the drawing, if the end portion 25A of the liquid fuel supply tube 25 is spaced from the inner peripheral surface 20 a of the liquid fuel tank 19. On the other hand, the liquid fuel 24 flows down the inner peripheral surface 20 a, if the end portion 25A of the liquid fuel supply tube 25 is in contact with the inner peripheral surface 20 a of the liquid fuel tank 19.

The liquid fuel tank 19 is provided within the cylindrical sprayer outer cylinder 27 in a concentric manner with the sprayer outer cylinder 27. In the liquid fuel tank 19, cylindrical space between the side portion 20 and sprayer outer cylinder 27 is an atomizing air passage 28 serving as an atomizing air passage. In the sprayer outer cylinder 27, an air inlet hole 29 is opened. The air inlet hole 29 is connected to an end portion 30A of the atomizing air supply tube 30. The base side of the atomizing air supply tube 30 is connected to an air supply blower of an unillustrated atomizing air supply system.

The two-fluid spray nozzle 38 is attached to a lower end portion 27A of the sprayer outer cylinder 27 and positioned under the liquid fuel tank 19. In other words, the two-fluid sprayer 12 is configured to include the liquid fuel tank 19, as a buffer for reducing fluctuations in flow rate of supplied fuel liquid, interposed between the liquid fuel supply tube 25 and two-fluid spray nozzle 38. The two-fluid spray nozzle 38 includes a disk-shaped nozzle body 39 and an atomizing air introduction portion 37 formed on the nozzle body 39 as an atomizing gas introduction portion. The two-fluid spray nozzle 38 is fixed to the lower end portion 27A of the sprayer outer cylinder 27 by fixing means such as welding, with the peripheral edge of the top surface of the nozzle body 39 abutted on the lower end surface of the sprayer outer cylinder 27 and with the atomizing air introduction portion 37 fitted into the lower end portion 27A of the sprayer outer cylinder 27.

The atomizing air introduction portion 37 is formed into a ring-shape and includes a space 41 with a circular plan view (top view) in the central part. The nozzle body 39 includes a reverse conical space (recess) 42 in the central part and a fine spray hole 44 opened at the center (at a vertex position of the reverse conical space 42). The space 41 of the atomizing air introduction portion 37 is continuous to the space 42 of the nozzle body 39, and the spaces 41 and 42 constitute a two-fluid converging space portion 43. Specifically, the two-fluid converging space portion 43 has a tapered structure with a circular top view and a diameter gradually reducing towards the spray hole 44. In the atomizing air introduction portion 37, grooves (slits) 40 are formed at two places in the circumference direction thereof. These grooves 40 are swirling type and are extended in tangent directions of the circumference of the two-fluid converging space portion 43 in a top view. Moreover, the grooves 40 are formed at positions rotationally symmetric (at equal intervals in the circumferential directions) around a central axis of the two-fluid converging space portion 43 (a central axis of the spray hole 44 in the example of the drawing).

On the other hand, the upper end portion 27B of the sprayer outer cylinder 27 is closed with a cap 31 as a closing member to prevent leak of the atomizing air from the inside of the sprayer outer cylinder 27 to the outside. The cap 31 is attached to the upper end portion 27B of the sprayer outer cylinder 27 by screwing a thread portion 33 formed in an outer peripheral surface of a lower portion 31A of the cap 31 to a thread portion 32 formed in an inner peripheral surface of the upper end portion 27B of the sprayer outer cylinder 27. Between a step portion 31B of the cap 31 and the upper end portion 27B of the sprayer outer cylinder 27, an O ring 34 is interposed to reliably prevent leak of the atomizing air. The end portion 25A of the liquid fuel supply tube 25 penetrates through the cap 31, passes through the inside of the sprayer outer cylinder 27 (the inside of a coil spring 36), and then inserted into the liquid fuel tank 19 through an upper end of the liquid fuel tank 19.

Between a washer 35 provided on an undersurface of the cap 31 and a washer 26 provided on an upper end of the liquid fuel tank 19, the coil spring 36 as a press member is interposed. The coil spring 36 presses the liquid fuel tank 19 downward to press an outer surface (undersurface) 21 b of the bottom portion 21 of the liquid fuel tank 19 against the top surface 37 a of the atomizing air introduction portion 37. Accordingly, the outer surface (undersurface) 21 b of the bottom portion 21 and top surface 37 a of the two-fluid nozzle 38 (atomizing air introduction portion 37) in contact with each other are firmly joined to each other, thus preventing formation of gap between these contact surfaces 21 b and 37 a.

Between the washer 26 and liquid fuel supply tube 25, a gap 45 is provided, through which internal space of the liquid fuel tank 19 and internal space of the sprayer outer cylinder 27 outside of the liquid fuel tank 19 communicate with each other. In other words, the upper end of the liquid fuel tank 19 is opened to the internal space of the sprayer outer cylinder 27, and the internal space of the liquid fuel tank 19 and the upper end portion (upstream portion) of the atomizing air passage 28 communicate with each other. Accordingly, pressure of atomizing air 46 flowing from the air inlet hole 29 into the sprayer outer cylinder 27 and then into the atomizing air passage 28 acts on the liquid level 23 of the liquid fuel 24 stored in the liquid fuel tank 19.

In this two-fluid sprayer 12, when the liquid fuel 24 for burner combustion which is fed from the liquid fuel supply pump through the liquid fuel supply tube 25 is discharged from the end portion 25A of the liquid fuel supply tube 25 (discharged continuously in the case of comparatively high flow rate and intermittently discharged in the case of comparatively low flow rate as illustrated in FIG. 5( a)), the liquid fuel 24 is once stored in the liquid fuel tank 19. The liquid fuel 24 stored in the liquid fuel tank 19 is continuously discharged from the liquid fuel discharge hole 22 of the bottom portion 21 of the liquid fuel tank 19 into the two-fluid converging space portion 43. In the case where the liquid fuel is intermittently discharged from the end portion 25A of the liquid fuel supply tube 25, a phenomenon is repeated in which the liquid level 23 rises while the liquid fuel 24 is discharged from the end portion 25A of the liquid fuel supply tube 25 and falls while the liquid fuel 24 is not discharged from the end portion 25A of the liquid fuel supply tube 25. Though the flow rate of the liquid fuel 24 discharged from the liquid fuel discharge hole 22 varies according to such fluctuations in liquid level, such variations in flow rate are much smaller than the conventional variations in flow rate.

On the other hand, the atomizing air 46 fed from an air supply pump through the atomizing air supply tube 30 flows into the sprayer outer cylinder 27 through the air inlet hole 29 and flows down the atomizing air passage 28 between the liquid fuel tank 19 and sprayer outer cylinder 27. Thereafter, the atomizing air 46 flows through the grooves 40 of the atomizing air introduction portion 37 of the two-fluid spray nozzle 38 to increase flow rate and is then introduced to the two-fluid converging space portion 43. The atomizing air 46 becomes swirling flow in the two-fluid converging space portion 43 and converges with (is mixed with) the liquid fuel 24 discharged from the liquid fuel discharge hole 22 of the liquid fuel tank 19. The liquid fuel 24 is therefore well mixed with the atomizing air 46 and is atomized with the atomizing air 46 to be sprayed together with the atomizing air 46 from the spray hole 44 of the two-fluid spray nozzle 38 into a combustion space 13 (flame) for combustion. The initial ignition to the atomized liquid fuel 24 is performed by a spark plug 54.

Herein, the liquid column head H of the liquid fuel 24 stored in the liquid fuel tank 19 is described in detail. The liquid column head H can be calculated by the following equation based on a pressure loss ΔP (hole) of the liquid fuel 24 flowing through the liquid fuel discharge hole 22, a kinetic energy E of the liquid fuel 24 discharged from the liquid fuel discharge hole 22, and a pressure loss ΔPair of the atomizing air 49 at the grooves 40.

Liquid Column Head H=Pressure Loss ΔP (hole)+Kinetic Energy E−Pressure Loss ΔPair

The kinetic energy E can be calculated by the following equation based on flow velocity v of the liquid fuel 24 and density ρ of the liquid fuel 24.

Kinetic Energy=ρv²/2

Moreover, the height of the liquid level 23 of the liquid fuel 24 stored in the liquid fuel tank 19 varies with the flow rate of the liquid fuel 24 supplied to the liquid fuel tank 19 through the liquid fuel supply tube 25. In other words, the liquid level 23 rises when the output of the fuel supply pump is controlled to increase the flow rate of the liquid fuel 24 supplied and falls when the flow rate of the liquid fuel 24 is reduced. Accordingly, the liquid fuel tank 19 is configured to have a height corresponding to changes in height of the liquid level 23 according to a predetermined regulation range of the flow rate of the supplied liquid fuel 24.

Moreover, the liquid fuel 24 is sprayed in a cone shape from the spray hole 44 as illustrated in FIG. 5( a). The spread of the spray (spray angle) is determined by a cross-sectional area of the grooves 40 (or flow speed of the atomizing air 46 flowing through the grooves 40), size of the spray hole 44 (or hole diameter), and the like.

Next, a description is given of the configuration other than the two-fluid sprayer 12 in detail. As shown in FIGS. 1 to 3, a cylindrical gas fuel supply tube 47 is provided so as to surround the periphery of the sprayer outer cylinder 27. The gas fuel supply tube 47 is concentrically provided with the sprayer outer cylinder 27, and cylindrical space between the gas fuel supply tube 47 and sprayer outer cylinder 27 is a gas fuel passage 14. Gas fuel 49 for burner combustion supplied from a gas fuel supply system flows down the gas fuel passage 14 to be sprayed from the lower end of the gas fuel passage 14 into the combustion space 13 for combustion. The liquid fuel 24 and the gas fuel 49 may be burned separately or simultaneously. Examples of the gas fuel 49 for burner combustion are methane, ethane, propane, butane, diethyl ether, and hydrogen. Furthermore, in the case of using the two-fluid spray burner 11 as a heat source of a reformer, the gas fuel 49 may be residual reformed gas not used for power generation in a fuel cell and returned to the two-fluid spray burner 11 (see FIG. 13).

The burner outer cylinder 48 is cylindrical and surrounds the periphery of the gas fuel supply tube 47. The burner outer cylinder 48 and gas fuel supply tube 47 are provided concentrically, and cylindrical space between the burner outer cylinder 48 and gas fuel supply tube 47 is a first combustion air passage 15. Accordingly, the combustion air 50 supplied from an air supply blower of the combustion air supply system flows down the combustion air passage 15.

Between the lower end portion of the combustion air passage 15, that is a lower end portion of the gas fuel supply tube 47, and the lower end portion of the burner outer cylinder 48, a plate 18 is provided. The plate 18 is a ring-shaped plate and separates the combustion air passage 15 and combustion space 13. In the example of the drawings, the plate 18 is provided at substantially the same height as that of the two-fluid spray nozzle 38, but it is not limited to this and may be provided at a position higher than that of the two-fluid spray nozzle 38. However, if the plate 18 is provided at a higher position, the first and second cylinders 16 and 17 need to be made longer than those of the example of the drawing. Accordingly, providing the plate 18 at the same height as that of the two-fluid spray nozzle 38 like the example of the drawing costs the least, which is reasonable.

The inner peripheral surface of the plate 18 is fixed to the outer peripheral surface of the gas fuel supply tube 47 by fixing means such as welding. In the outer peripheral surface of the plate 18, a plurality of protrusions 51 (four protrusions in the example of FIG. 2) are formed. End surfaces of the protrusions 51 are fixed to the inner peripheral surface of the burner outer cylinder 48 by fixing means such as welding. Accordingly, part between the gas fuel supply tube 47 and the vicinity of the burner outer cylinder 48 is closed by the plate 18. However, on the outer periphery of the plate 18, gaps are formed between the outer peripheral surface of the plate 18 and the inner peripheral surface 48 a of the burner outer cylinder 48 by the protrusions 51. These gaps are combustion air holes 52. In other words, the combustion air passage 15 and combustion space 13 communicate with each other through these combustion air holes 52.

Accordingly, after flowing down the combustion air passage 15, the combustion air 50 is blocked by the plate 18 to be introduced to the outer peripheral side of the plate 18, which is away from the two-fluid spray nozzle 38 (spray hole 44) and flows through the combustion air holes 52 into the combustion space 13.

Moreover, the first cylinder 16 extending downward and the second cylinder 17 extending downward, the second cylinder 17 being provided inside the first cylinder 16, are fixed to the undersurface of the plate 18 by fixing means such as welding. The first cylinder 16 is located in a position inner to the combustion air holes 52 and arranged concentrically with the burner outer cylinder 48. The cylindrical space between the burner outer cylinder 48 and the first cylinder 16 is a second combustion air passage 53.

Accordingly, after flowing down the first combustion air passage 15 and passing through the combustion air hole 52, the combustion air 50 further flows down the second combustion air passage 53. The combustion air 50 is discharged from the lower end of the combustion air passage 53 and spreads over the combustion space 13. Accordingly, a part of the combustion air 50 discharged from the combustion air passage 53 (for example, about 30% of the entire combustion air 50) is supplied to (mixed with) the liquid fuel 24 sprayed from the two-fluid sprayer 12 (the two-fluid spray nozzle 38) at a position downward away from the plate 18 and used in combustion of the liquid fuel 24. The amount of the combustion air 50 mixed with the liquid fuel 24 is set so that an average of the air ratio is not more than 1.5, for example. The residual of the combustion air 50 discharged from the combustion air passage 53 (for example, about 70% of the entire combustion air 50) further flows down and is mixed with combustion exhaust gas produced by the combustion, thus producing a large amount of combustion exhaust gas.

The first cylinder 16 is installed for the purpose of delaying supply of a part of the combustion air 50 to the atomized liquid fuel 24, that is, supplying the combustion air 50 to the atomized liquid fuel 24 at the position downward away from the plate 18. Thus, the plate 18 is kept away of the flame and prevented from being sooted. The length of the first cylinder 16, that is the end position (bottom end) of the first cylinder 16 may be properly set based on a relation with size of the plate 18 (distance between the spray hole 44 of the two-fluid spray nozzle 38 and the combustion air hole 52).

In other words, even without the first cylinder 16 but only with the plate 18 and the combustion air hole 52 in the outer periphery of the plate 18, a part of the combustion air 50 passed through the combustion air hole 51 is supplied to the atomized liquid fuel 24 at a position downward away from the plate 18. The longer the distance between the spray hole 44 and the combustion air hole 52 is, the farther, from the plate 18, the position where the part of the combustion air 50 is supplied to the atomized liquid fuel 24 is. If the plate 18 is increased in size to increase the distance between the spray hole 44 and the combustion air hole 52, the two-fluid spray burner 11 is increased in diameter.

On the other hand, when the distance between the spray hole 44 and the combustion air hole 52 is limited by the limitation in size of the two-fluid spray burner 11, the supply of the part of the combustion air 50 to the atomized liquid fuel 24 cannot be delayed enough in some cases only by providing the plate 18 and combustion air hole 51. In such a case, provision of the first cylinder 16 as illustrated in the drawing is very effective. In this case, as the distance between the spray hole 44 and the combustion air hole 52 is reduced, the first cylinder 16 is extended downward. However, to prevent interference between the first cylinder 16 and sprayed liquid fuel 24, the end (lower end) of the first cylinder 16 needs to be positioned outside of (above) a contour 24A of the sprayed liquid fuel 24. In other words, the end (lower end) of the first cylinder 16 cannot be extended more than the contour 24A of the sprayed liquid fuel 24.

If the distance between the spray hole 44 and the combustion air hole 52 is reduced, the installation position of the first cylinder 16 becomes closer to the spray hole 44, and the distance between the plate 18 and contour 24A of the atomized liquid fuel 24 is reduced. The first cylinder 16 therefore cannot be made so long. The distance between the spray hole 44 and the combustion air hole 52 and the length of the first cylinder 16 (including necessity of the first cylinder 16) may be properly determined in view of such restrictions.

The second cylinder 17 is positioned inside the first cylinder 16 and is provided concentrically with the first cylinder 16. The second cylinder 17 is provided for the purpose of preventing stagnation (convection) of the atomized liquid fuel 24 from occurring near the plate 18. Thus, the plate 18 is kept away of the flame and prevented from being sooted. Accordingly, the second cylinder 17 is extended downward as much as possible. However, to prevent interference between the second cylinder 17 and atomized liquid fuel 24, the end (lower end) of the second cylinder 17 needs to be positioned outside of (above) the contour 24A of the atomized liquid fuel 24. In other words, the end (lower end) of the second cylinder 17 also can only be extended to the contour 24A of the atomized liquid fuel 24 at maximum.

For example, as shown in FIG. 1, length L2 between the end (bottom end) of the two-fluid spray nozzle 38 (spray hole 44) and the end (bottom end) of the second cylinder 17 needs to satisfy 0<L2<L1 tan θ. Herein, L1 is the distance between the spray hole 44 of the two-fluid spray nozzle 38 and the second cylinder 17, and θ is an angle between the contour 24A of the sprayed liquid fuel 24 and the horizontal line thereof. The entire length of the second cylinder 17 is L2 added to length between the undersurface of the plate 18 and the end (lower end) of the two-fluid spray nozzle 38 (spray hole 44). Such a condition is also applied to length between the end (lower end) of the two-fluid spray nozzle 38 (spray hole 44) and the end (lower end) of the second cylinder 17 and the entire length of the first cylinder 16. The distance between the spray hole 44 of the two-fluid spray nozzle 38 and the second cylinder 16 is configured to be for example, not less than 50 or 60 times the diameter of the spray hole 44 (about 1 mm, for example).

As described above, the two-fluid spray burner 11 of present Embodiment 1 is provided with the liquid fuel tank 19 which includes the cylindrical side portion 20 and the bottom portion 21 provided at the lower end of the side portion 20 and stores the liquid fuel 24 supplied from the liquid fuel supply tube 25. The liquid fuel tank 19 is configured to allow the stored liquid fuel 24 to be discharged from the liquid fuel discharge hole 22, in the bottom portion 21, which is opened below the liquid level of the stored liquid fuel 24. The liquid fuel 24 discharged from the liquid fuel discharge hole 22 of the liquid fuel tank 19 is atomized with the atomizing air 46 and is burned. Accordingly, even when the liquid fuel 24 is intermittently supplied from the liquid fuel supply tube 24 to the liquid fuel tank 19, the liquid fuel stored in the liquid fuel tank 19 is continuously discharged from the liquid fuel discharge hole 22 of the liquid fuel tank 19. In other words, even when the supply flow rate of the pump of the liquid fuel supply system is reduced and the liquid fuel 24 is intermittently supplied from the liquid fuel supply tube 25 to the liquid fuel tank 19, the liquid level 23 of the liquid fuel 24 stored in the liquid fuel tank 19 fluctuates just a little up and down and only causes the flow rate of the liquid fuel 24 discharged from the liquid fuel discharge hole 22 to fluctuate a little. The flow rate of supplied liquid fuel does not fluctuate as much as the conventional one. It is therefore possible to stably supply the liquid fuel 24 even if the flow rate of the liquid fuel supplied is low, thus facilitating achievement of stable combustion and eliminating the possibility of producing unburned exhausted gas and causing accidental fire.

According to the two-fluid spray burner 11 of Embodiment 1, the two-fluid spray burner 11 is configured so that the liquid fuel 22 discharged from the liquid fuel discharge hole 22 and flown into the two-fluid converging space portion 43 converges with the atomizing air flowing down the atomizing air passage 28 and flown through the grooves 40 at the atomizing air introduction portion 37 to be introduced into the two-fluid converging space portion 43 and then sprayed from the spray hole 44 together with the atomizing air. Accordingly, the liquid fuel 24 is well mixed with the atomizing air 46 with the flow speed increased at the grooves 40 (with the horizontal speed component increased) at the two-fluid converging space portion 43 and then sprayed from the spray hole 44 of the two-fluid spray nozzle 38. Compared to the case of not providing the two-fluid converging space portion 43 and grooves 40, therefore, the spread angle of the liquid fuel 24 is larger, and the liquid fuel 24 is surely atomized, so that the combustion quality is improved.

According to the two-fluid spray burner 11 of Embodiment 1, the grooves 40 of the atomizing air introduction portion 37 are formed along the tangent directions of the circumference of the two-fluid converging space portion 43 in a top view. Accordingly, the atomizing air 46 is swirled and mixed with the liquid fuel 24 at the two-fluid converging space portion 43. The liquid fuel 24 and atomizing air 46 are therefore mixed more surely. The liquid fuel 24 sprayed from the spray hole 44 of the two-fluid spray nozzle 38 can be therefore more surely atomized, and the combustion quality of the liquid fuel 24 can be further improved.

According to the two-fluid spray burner 11 of Embodiment 1, the plurality of grooves 40 of the atomizing air introduction portion 37 are formed at positions rotationally symmetric around the central axis of the two-fluid converging space portion 43. Accordingly, the circumferential distribution of the liquid fuel 24 sprayed from the spray hole 44 of the two-fluid spray nozzle 38 can be equalized, and thus improving the combustion characteristics of the liquid fuel 24.

Moreover, the two-fluid spray burner 11 of Embodiment 1 is provided with the coil spring 36 pressing the liquid fuel tank 19 downward. The bottom portion 21 of the liquid fuel tank 19 is therefore pressed against the atomizing air introduction portion 37 of the two-fluid spray nozzle 38 to be brought into firm contact. Accordingly, the undersurface 21 b of the bottom portion 21 of the fuel tank 19 and the top surface 37 a of the atomizing air introduction portion 37 are firmly in contact to each other to prevent gap between these contact surfaces 21 b and 37 a. It is therefore possible to prevent the atomizing air 46 from flowing into portion other than the grooves 40 and allow the effect of wide spray by the grooves 40 to be sufficiently exerted.

Moreover, according to the two-fluid spray burner 11 of Embodiment 1, the two-fluid converging space portion 43 is reversed conical, and the spray hole 44 is formed at the vertex position of the reverse conical space 43. Accordingly, the liquid fuel 24 and atomizing air 46 can be surely mixed at the two-fluid converging space portion 43. The liquid fuel 24 to be sprayed from the spray hole 44 is more surely atomized, thus further improving the combustion characteristics of the liquid fuel 24.

Moreover, according to the two-fluid spray burner 11 of Embodiment 1, the two-fluid spray burner 11 is configured so that the cylindrical gas fuel passage 14 is formed between the sprayer outer cylinder 27 and the gas fuel supply tube 47 surrounding the sprayer outer cylinder 27 and allows the gas fuel 49 to flow down the gas fuel passage 14 to be sprayed from the lower end of the gas fuel passage 14 and burned. Accordingly, the gas fuel 49 sprayed from the cylindrical gas fuel passage 14 is circumferentially uniform. It is therefore possible to improve the combustion characteristics, thus achieving a flame holding effect by the gas fuel 49 when the liquid fuel 24 is supplied at a low flow rate, for example.

Moreover, in the two-fluid spray burner 11 of Embodiment 1, in the case where the end portion 25A of the liquid fuel supply tube 25 is in contact with the internal peripheral surface 20 a of the side potion 20 of the liquid fuel tank 19, the liquid fuel 24 flows down the internal peripheral surface 20 a even when the flow rate of the liquid fuel 24 discharged from the liquid fuel supply tube 25 is low. It is therefore possible to achieve more stable discharge of the liquid fuel 24 from the liquid fuel discharge hole 22. In other words, when the liquid fuel 24 falls in droplets, the liquid level 23 of the liquid fuel 24 stored in the liquid fuel tank 19 greatly fluctuates. In the case where the liquid level 23 is very low, it can be thought that the liquid fuel discharge hole 22 is temporarily exposed and discharge of the liquid fuel 24 is stopped. However, allowing the liquid fuel 24 to flow down along the inner peripheral surface 20 a of the liquid fuel tank 19 can prevent occurrence of such a disadvantage.

Furthermore, according to the two-fluid spray burner 11 of Embodiment 1, the two-fluid spray burner 11 is configured so that after flowing down the combustion air passage 15, the combustion air 50 is blocked by the plate 18 and is introduced to the outer peripheral side of the plate 18, away from the two-fluid spray nozzle 38, to flow through the combustion air hole 52 into the combustion space 13. Accordingly, only a part of the combustion air 50 is mixed with the liquid fuel 24 sprayed from the two-fluid spray nozzle 38 at the combustion space 13 and used in combustion of the liquid fuel 24, and the residual of the combustion air 50 further flows down and is mixed with the combustion exhausted gas produced by the combustion. It is therefore possible to achieve proper mixture of the combustion air 50 and liquid fuel 24 through one supply of the combustion air (one step) and produce a large amount of combustion exhaust gas without exceedingly cooling flame. In other words, it is possible to achieve a burner such as a two-fluid spray burner which is capable of producing a large amount of combustion exhaust gas with a simple configuration and does not cause generation of unburned gas and accidental fire.

Moreover, the combustion air 50 is caused by the plate 18 to flow into the combustion space 13 at the position away from the two-fluid spray nozzle 38. Accordingly, the position where a part of the combustion air 50 is supplied to fuel can be set downward away from the plate 18. The position of flame is therefore downward away from the plate 18, thus preventing adherence of soot to the undersurface of the plate 18. Although a lot of soot adhering to the undersurface of the plate 18 may cause disadvantages such as clogging of the two-fluid spray nozzle 38 due to the soot and abnormal heating of the two-fluid sprayer 12 due to the soot absorbing radiation heat from flame, by preventing soot from sticking to the undersurface of the plate 18 as described above, such disadvantages can be prevented from occurring.

Moreover, according to the two-fluid spray burner 11 of Embodiment 1, the two-fluid spray burner 11 is configured so that the first cylinder 16 extending downward from the undersurface of the plate 18 for delaying supply of the combustion air is provided, and the cylindrical combustion air passage 53 communicating with the combustion air hole 52 is formed between the first cylinder 16 and the burner outer cylinder 48. The combustion air 50 passing through the combustion air hole 52 is thus allowed to flow down the combustion air passage 53 and then flow into the combustion space 13 from the lower end of the combustion air passage 53. It is therefore possible to delay supply of a part of the combustion air 50 to the liquid fuel 24 sprayed from the two-fluid spray nozzle 38. In other words, the position where a part of the combustion air 50 is supplied to the liquid fuel 24 can be set downward away from the plate 18. Accordingly, the position of flame is set downward away from the plate 18, thus preventing soot from sticking to the undersurface of the plate 18.

It is possible to obtain the operational effect of setting the position where the part of the combustion air 50 is supplied to the liquid fuel 24 downward away from the plate 18 by provision of only the plate 18 as described above. However, as described in Embodiment 1, by providing the first cylinder 16 for delaying supply of the combustion air, the position where a part of the combustion air 50 is supplied to the liquid fuel 24 can be more surely set downward away from the plate 18.

Moreover, when the plate 18 cannot be made large so much because of limitation on size of the two-fluid spray burner 11 and the like, and the distance between the two-fluid spray nozzle 38 and combustion air hole 52 cannot be made long enough, the part of the combustion air 50 supplied to the liquid fuel 24 becomes excessive, and the flame may be excessively cooled. On the contrary, by providing the first cylinder 16 for delaying supply of combustion air as shown in Embodiment 1, not only the position where the part of the combustion air 50 is supplied to the liquid fuel 24 can be set downward away from the plate 18, but also the amount of the part of the combustion air 50 supplied to the liquid fuel 24 can be reduced to a proper amount. Accordingly, in such a view, provision of the first cylinder 16 like Embodiment 1 is effective. By providing the first cylinder 16, the plate 18 can be reduced in size, and the two-fluid spray burner 11 can be miniaturized.

Moreover, according to the two-fluid spray burner 11 of Embodiment 1, the second cylinder 17 extending from the undersurface of the plate 18 for preventing stagnation is provided within the first cylinder 16 for delaying supply of combustion air. Accordingly, stagnation (convection) of the liquid fuel 24 can be prevented from occurring near the undersurface of the plate 18 by the second cylinder 17 for preventing stagnation. It is therefore possible to prevent the liquid fuel 24 stagnating near the undersurface of the plate 18 from catching fire and soot from sticking to the undersurface of the plate 18.

Moreover, according to the two-fluid spray burner 11 of Embodiment 1, by surrounding flame with the burner outer cylinder 48, flame (the sprayed liquid fuel 24) and the combustion air 50 can be well mixed in the combustion space 13, thus improving the combustion characteristics.

Embodiment 2

FIG. 6( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 2 of present invention, and FIG. 6( b) is a top view showing a two-fluid spray nozzle provided for the two-fluid sprayer (a view in a direction of arrows E of FIG. 6( a)).

As shown in FIGS. 6( a) and 6(b), in a two-fluid spray nozzle 38 of a two-fluid sprayer 12 in Embodiment 2, grooves (slits) 61 are formed at four places in the circumference of the atomizing air introduction portion 37. These grooves 61 are collision type. The grooves 61 are individually extended in radial directions of the two-fluid converging space portion 43 having a circular top view and are formed at positions rotationally symmetric (circumferentially at equal intervals) around the central axis of the two-fluid converging space portion 43 (the central axis of the spray hole 44 in the example of the drawing).

In the two-fluid sprayer 21, after flowing down the atomizing air passage 28, the atomizing air 46 flows through the grooves 61 of the atomizing air introduction portion 37 in the two-fluid spray nozzle 38 to increase in flow speed and is introduced into the two-fluid converging space portion 43. The atomizing air 46 collides and converges (is mixed) with the liquid fuel 24 discharged from the liquid fuel discharge hole 22 of the liquid fuel tank 19 at the two-fluid converging space portion 43. The liquid fuel 24 and atomizing air 46 are thus well mixed, and the liquid fuel 24 is atomized with the atomizing air 46 and then sprayed from the spray hole 44 of the two-fluid spray nozzle 38 together with the atomizing air 46 into the combustion space 13.

The configuration of the other parts of the two-fluid sprayer 12 of FIG. 6 is the same as that of the two-fluid sprayer 12 of FIG. 4. The configuration of the parts other than the two-fluid sprayer of the two-fluid spray burner of Embodiment 2 is the same as that of the two-fluid spray burner 11 of FIGS. 1 to 3.

According to the two-fluid spray burner of Embodiment 2, the following operational effects can be obtained, and in addition, the same operational effects as those of the aforementioned Embodiment 1 can be obtained.

Specifically, according to the two-fluid spray burner of Embodiment 2, by forming the grooves 61 of the atomizing gas introduction portion 37 along the radial directions of the two-fluid converging space portion 43 in the top view, the atomizing air 46 collides with the liquid fuel 24 at the two-fluid converging space portion 43 to be mixed with the liquid fuel 24. Accordingly, the liquid fuel 24 and atomizing air 46 are more surely mixed. The liquid fuel 24 sprayed from the spray hole 44 of the two-fluid spray nozzle 38 can be atomized more surely, thus further improving the combustion characteristics of the liquid fuel 24.

Furthermore, the plurality of grooves 61 of the atomizing gas introduction portion 37 are formed at positions rotationally symmetric around the central axis of the two-fluid converging space portion 43. Accordingly, the distribution of the liquid fuel 24 sprayed from the spray hole 44 of the two-fluid spray nozzle 38 can be uniformed in the circumferential direction, thus improving the combustion characteristics of the liquid fuel 24.

Embodiment 3

FIG. 7 (a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 3 of present invention, and FIG. 7( b) is a top view showing a two-fluid spray nozzle provided for the two-fluid sprayer (a view in a direction of an arrow F of FIG. 7( a))

As shown in FIG. 7, in the two-fluid sprayer 12 in Embodiment 3, the inner surface (top surface) 21 a of the bottom portion 21 of the liquid fuel tank 19 is a tapered (reverse conical) surface, and the fine liquid fuel discharge hole 22 is formed at the center (at the vertex position of the reverse conical tapered surface). In the outer surface (undersurface) 21 b of the bottom portion 21 of the liquid fuel tank 19, an outside portion 21 b-1 composed of a tapered (reverse truncated conical) surface, and an inside portion 21 b-2 is composed of a circular horizontal surface.

On the other hand, the atomizing air introduction portion 37 of the two-fluid spray nozzle 38 is formed in a ring-shape, and an inner peripheral surface 37 b thereof is composed of a tapered (reverse truncated cone-shaped) surface. The liquid fuel tank 19 is installed on the atomizing air introduction portion 37 with the outside portion 21 b-1 (tapered surface portion) of the undersurface 21 b of the bottom portion 21 being abutted and fitted into the inner peripheral surface 37 b (tapered surface portion) of the atomizing air introduction portion 37. In this case, the liquid fuel tank 19 is pressed downward by the coil spring 36 (see FIG. 4), and the outside portion 21 b-1 (tapered surface portion) of the undersurface 21 b of the bottom portion 21 of the liquid fuel tank 19 is therefore pressed against the inner peripheral surface 37 b (tapered surface portion) of the atomizing air introduction portion 37 for a tight close contact, thus preventing gap between these contact surfaces 21 b-1 and 37 b.

The nozzle body 39 of the two-fluid spray nozzle 38 includes a reverse conical space (recess) 42 formed in the central part, and the fine spray hole 44 is formed at the center (at the vertex position of the reverse conical space 42). The space 41 of the atomizing air introduction portion 37 and the space 42 of the nozzle body 39 are continuous to each other and constitute the two-fluid converging space portion 43. In other words, the two-fluid converging space portion 43 has a circular plan view (top view) and has a tapered structure with the diameter thereof gradually reduced towards the spray hole 44. In the atomizing air introduction portion 37, the grooves (slits) 40 are formed at two places in the circumference thereof. These grooves 40 are swirling type like the grooves 40 of FIG. 5 and are extended in tangent directions of the circumference of the two-fluid converging space portion 43 in a top view. Moreover, the grooves 40 are formed at positions rotationally symmetric around a central axis of the two-fluid converging space portion 43 (circumferentially at equal intervals). The grooves formed at the atomizing air introduction portion 37 are not limited to the swirling type but may be collision type like that of FIG. 6.

The configuration of the other parts of the two-fluid sprayer 12 of FIG. 7 is the same in that of the two-fluid sprayer 12 of FIG. 4. The configuration of the parts other than the two-fluid sprayer of the other part of the two-fluid spray burner of Embodiment 3 is the same as that of the two-fluid spray burner 11 of FIGS. 1 to 3.

According to the two-fluid spray burner of Embodiment 3, the following operational effects can be obtained, and in addition, the same operational effects as those of the aforementioned Embodiments 1 and 2 can be obtained.

Specifically, according to the two-fluid spray burner of Embodiment 3, the liquid fuel tank 19 is installed on the atomizing gas introduction portion 37 with the tapered surface portion (the outside portion 21 b-1 of the undersurface 21 b of the bottom portion 21) of the liquid fuel tank 19 being abutted and fitted to the tapered surface portion (inner peripheral surface 37 b) of the atomizing gas introduction portion 37. It is therefore easy to align the central axes of the liquid fuel tank 19 and two-fluid spray nozzle 38. Accordingly, the liquid fuel tank 19 is installed at the center. The width of the atomizing air passage 28 can be therefore made uniform in circumferential direction, so that the flow of the atomizing air 46 in the atomizing air passage 28 can be made uniform in the circumferential direction. This makes it possible to hold the symmetric properties of the liquid fuel 24 (or symmetric properties of the flame) sprayed from the spray hole 44 of the two-fluid spray nozzle 38.

Moreover, according to the two-fluid spray burner of Embodiment 3, by pressing the liquid fuel tank 19 downward by the coil spring 36 (see FIG. 4), the bottom portion 21 of the liquid fuel tank 19 is pressed against the atomizing air introduction portion 37 of the two-fluid spray nozzle 38 to bring the tapered surface portion (outside portion 21 b-1) of the bottom portion 21 of the fuel tank 19 and the tapered surface portion (inner peripheral surface 37 b) of the atomizing air introduction portion 37 into firm contact, thus preventing gap between these contact surfaces 21 b-1 and 37 b. It is therefore possible to prevent the atomizing air 46 from flowing into portions other than the grooves 40, thus allowing the effect of the wide spray by the grooves 40 to be sufficiently exerted.

Embodiment 4

FIG. 8( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 4 of the present invention (a longitudinal sectional view taken along a line G-G of FIG. 8( b)); FIG. 8( b) is a bottom view showing a liquid fuel tank provided for the two-fluid sprayer (a view in a direction of an arrow H of FIG. 8( a)); FIG. 8( c) is a view in a direction of an arrow I of FIG. 8( b); and FIG. 8( d) is a transverse sectional view taken along a line J-J of FIG. 8( a).

As shown in FIG. 8, in the two-fluid sprayer 12 of Embodiment 4, the inner surface (top surface) 21 a of the bottom portion 21 of the liquid fuel tank 19 is composed of a tapered (reverse conical) surface, and the fine liquid fuel discharge hole 22 is formed at the center (at the vertex position of the reverse conical tapered surface). Moreover, in the outer surface (undersurface) 21 b of the bottom portion 21 of the liquid fuel tank 19, the outside portion 21 b-1 is composed of a tapered (reverse truncated cone-shaped) surface, and an inside portion 21 b-2 is composed of a circular horizontal surface.

On the other hand, the two-fluid spray nozzle 38 does not include an atomizing air introduction portion (see FIG. 7) and is integrally formed with the sprayer outer cylinder 27 at the lower end of the sprayer outer cylinder 27 (a separate body may be fixed by welding or the like). The two-fluid spray nozzle 38 has the inner surface (top surface) 38 a which is composed of a tapered (reverse conical) surface. The liquid fuel tank 19 is installed on the two-fluid spray nozzle 38 with the outside portion 21 b-1 (tapered surface portion) of the undersurface 21 b of the bottom portion 21 being abutted and fitted to the inner surface 38 a (tapered surface portion) of the two-fluid spray nozzle 38. In this case, the liquid fuel tank 19 is pressed downward by the coil spring 36 (see FIG. 4), so that the outside portion 21 b-1 (tapered surface portion) of the undersurface 21 b of the bottom portion 21 of the liquid fuel tank 19 is pressed against the inner surface 38 a (tapered surface portion) of the two-fluid spray nozzle 38 to be brought into firm contact, thus preventing gap between these contact surfaces 21 b-1 and 38 b.

A reverse conical space formed by the inner surface 38 a of the tapered structure in the central part of the two-fluid spray nozzle 38 serves as the two-fluid converging space portion 43. The fine spray hole 44 is formed at the center (the vertex position of a reverse conical space 43) of the two-fluid converging space portion 43 and communicates with the two-fluid converging space portion 43. Specifically, the two-fluid converging space portion 43 has a circular plan view (top view) and has a tapered structure with the diameter thereof gradually reduced towards the spray hole 44.

In the undersurface 21 b side of the bottom portion 21 of the liquid fuel tank 19, grooves (slits) 71 are formed at two places in the circumference thereof. These grooves 71 are swirling type and are extended in tangent directions of the circumference of the two-fluid converging space portion 43 in a top view. Moreover, the grooves 71 are formed at positions rotationally symmetric around a central axis of the two-fluid converging space portion 43 (circumferentially at equal intervals).

Accordingly, after flowing down the atomizing air passage 28, the atomizing air 46 flows through the grooves 71 of the bottom portion 21 of the liquid fuel tank 19 to increase in flow rate and is then introduced to the two-fluid converging space portion 43. The atomizing air 46 becomes swirling flow in the two-fluid converging space portion 43 and converges (is mixed) with the liquid fuel 24 discharged from the liquid fuel discharge hole 22 of the liquid fuel tank 19. The liquid fuel 24 and atomizing air 46 are thus well mixed, and the liquid fuel 24 is atomized with the atomizing air 46 and sprayed from the spray hole 44 of the two-fluid spray nozzle 38 into a combustion space 13.

The configuration of the other parts of the two-fluid sprayer 12 of FIG. 8 is the same as that of the two-fluid sprayer 12 of FIG. 4. The configuration of the parts other than the two-fluid sprayer of the two-fluid spray burner of Embodiment 3 is the same as that of the two-fluid spray burner 11 of FIGS. 1 to 3.

According to the two-fluid spray burner of Embodiment 3, the following operational effects can be obtained, and in addition, the same operational effects as those of the aforementioned Embodiment 1 can be obtained.

According to the two-fluid spray burner of Embodiment 4, the two-fluid spray burner is configured so that the liquid fuel 24 which is discharged from the liquid fuel discharge hole 44 and flows into the two-fluid converging space portion 43 converges at the two-fluid converging space portion 43 with the atomizing air 46 flowing down the atomizing air passage 28 and then flowing through the grooves 71 at the bottom portion 21 of the liquid fuel tank 19 to be introduced into the two-fluid converging space portion 43 and then is sprayed from the spray hole 44 together with the atomizing air 46. Accordingly, the liquid fuel 24 is well mixed with the atomizing air 46 whose the flow rate is increased through the grooves 71 (with the horizontal speed component increased) at the two-fluid converging space portion 43 and then sprayed from the spray hole 44. Accordingly, compared to the case of not providing the two-fluid converging space portion 43 and grooves 71, the spread angle of the sprayed liquid fuel 24 is larger, and the liquid fuel 24 is surely atomized, thus improving the combustion characteristics of the liquid fuel 24.

Furthermore, the liquid fuel tank 19 is installed on the two-fluid spray nozzle 38 with the tapered surface portion (the outside portion 21 b-1 of the undersurface 21 b of the bottom portion 21) of the liquid fuel tank 19 abutted and fitted to the tapered surface portion (inner surface 38 a) of the two-fluid spray nozzle 38. Thus, it is easy to align the central axes of the liquid fuel tank 19 and two-fluid spray nozzle 38. Accordingly, the liquid fuel tank 19 is installed at the center. The width of the atomizing air passage 28 can be therefore made uniform in circumferential direction, so that the flow of the atomizing air 46 in the atomizing air passage 28 can be made uniform in the circumferential direction. It is therefore possible to secure the symmetric properties of the liquid fuel 24 (or symmetric properties of flame) sprayed from the spray hole 44 of the two-fluid spray nozzle 38.

Moreover, the grooves 71 of the bottom portion 21 of the liquid fuel tank 19 are formed along the tangent directions of the circumference of the two-fluid converging space portion 43 in a top view. Accordingly, the atomizing air 46 is swirled and mixed with the liquid fuel 24 at the two-fluid converging space portion 43. The liquid fuel 24 and atomizing air 46 are thus mixed more surely. The liquid fuel 24 sprayed from the spray hole 44 of the two-fluid spray nozzle 38 can be therefore surely atomized, thus improving the combustion characteristics of the liquid fuel 24.

Moreover, the plurality of grooves 71 of the bottom portion 21 of the liquid fuel tank 19 are formed at positions rotationally symmetric around the central axis of the two-fluid converging space portion 43. Accordingly, the liquid fuel 24 sprayed from the spray hole 44 of the two-fluid spray nozzle 38 is uniformly distributed in the circumferential direction, thus improving the combustion characteristics of the liquid fuel 24.

According to the two-fluid spray burner of Embodiment 4, by pressing the liquid fuel tank 19 downward by the coil spring 36 (see FIG. 4), the bottom portion 21 of the liquid fuel tank 19 is pressed against the two-fluid spray nozzle 38, so that the tapered surface portion (outside portion 21 b-1) of the bottom portion 21 of the fuel tank 19 and the tapered surface portion (inner surface 38 a) of the two-fluid spray nozzle 38 are brought into firm contact, thus preventing gap between these contact surfaces 21 b-1 and 38 a. It is therefore possible to prevent the atomizing air 46 from flowing into portions other than the grooves 71, thus allowing the effect of the wide spray by the grooves 71 to be sufficiently exerted.

Embodiment 5

FIG. 9( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 5 (a longitudinal sectional view taken along a line K-K of FIG. 9( b)); FIG. 9( b) is a bottom view showing a liquid fuel tank provided for the two-fluid sprayer (a view in a direction of an arrow L of FIG. 9( a)); and FIG. 9 (c) is a transverse sectional view taken along a line M-M of FIG. 9( a).

As shown in FIG. 9, in the two-fluid sprayer 12 of Embodiment 5, the inner surface (top surface) 21 a of the bottom portion 21 of the liquid fuel tank 19 is composed of a tapered (reverse conical) surface, and the fine liquid fuel discharge hole 22 is formed at the center (at the vertex position of the reverse conical tapered surface). Moreover, in the outer surface (undersurface) 21 b of the bottom portion 21 of the liquid fuel tank 19, the outside portion 21 b-1 is composed of a tapered (reverse truncated cone-shaped) surface, and an inside portion 21 b-2 is composed of a circular horizontal surface.

On the other hand, the two-fluid spray nozzle 38 does not include an atomizing air introduction portion (see FIG. 7) and is integrally formed with the sprayer outer cylinder 27 at the lower end of the sprayer outer cylinder 27 (a separate body may be fixed by welding or the like). The two-fluid spray nozzle 38 has the inner surface (top surface) 38 a which is composed of a tapered (reverse conical) surface. The liquid fuel tank 19 is installed on the two-fluid spray nozzle 38 with the outside portion 21 b-1 (tapered surface portion) of the undersurface 21 b of the bottom portion 21 abutted and fitted to the inner surface 38 a (tapered surface portion) of the two-fluid spray nozzle 38. In this case, the liquid fuel tank 19 is pressed downward by the coil spring 36 (see FIG. 4), so that the outside portion 21 b-1 (tapered surface portion) of the undersurface 21 b of the bottom portion 21 of the liquid fuel tank 19 is pressed against the inner surface 38 a (tapered surface portion) of the two-fluid spray nozzle 38 and brought into firm contact, thus preventing gap between these contact surfaces 21 b-1 and 38 b.

A reverse conical space formed by the inner surface 38 a with the tapered structure in the central part of the two-fluid spray nozzle 38 serves as the two-fluid converging space portion 43. The fine spray hole 44 is formed at the center (the vertex position of the reverse conical space 43) of the two-fluid converging space portion 43 and communicates with the two-fluid converging space portion 43. Specifically, the two-fluid converging space portion 43 has a circular plan view (top view) and has a tapered structure with the diameter thereof gradually reduced towards the spray hole 44.

In the undersurface 21 b side of the bottom portion 21 of the liquid fuel tank 19, grooves (slits) 81 are formed at four places in the circumference thereof. These grooves 81 are the collision type and are extended in radial directions of the two-fluid converging space portion 43 in a top view and are formed at positions rotationally symmetric around the central axis of the two-fluid converging space portion 43 (circumferentially at equal intervals).

After flowing down the atomizing air passage 28, the atomizing air 46 flows through the grooves 81 at the bottom portion 21 of the liquid fuel tank 19 to increase in flow speed and then introduced to the two-fluid converging space portion 43. The atomizing air 46 collides and converges (is mixed) with the liquid fuel 24 discharged from the liquid fuel discharge hole 22 of the liquid fuel tank 19 at the two-fluid converging space portion 43. The liquid fuel 24 and atomizing air 46 are thus well mixed, and the liquid fuel 24 is atomized with the atomizing air 46 and then sprayed from the spray hole 44 of the two-fluid spray nozzle 38 together with the atomizing air 46 into the combustion space 13.

The configuration of the other parts of the two-fluid sprayer 12 of FIG. 9 is the same as that of the two-fluid sprayer 12 of FIG. 4. The configuration of the parts other than the two-fluid sprayer of the two-fluid spray burner of Embodiment 5 is the same as that of the two-fluid spray burner 11 of FIGS. 1 to 3.

According to the two-fluid spray burner of Embodiment 5, the same operational effects as those of the aforementioned Embodiment 4 can be obtained, and in addition, the same operational effects as those of the aforementioned Embodiment 1 can be obtained.

According to the two-fluid spray burner of Embodiment 5, the two-fluid spray burner is configured so that the liquid fuel 24 which is discharged from the liquid fuel discharge hole 44 and flows into the two-fluid converging space portion 43 converges at the two-fluid converging space portion 43 with the atomizing air 46 which flows down the atomizing air passage 28 and then flows through the grooves 81 at the bottom portion 21 of the liquid fuel tank 19 and then is introduced into the two-fluid converging space portion 43 to be sprayed from the spray hole 44 together with the atomizing air 46. The liquid fuel 24 is therefore well mixed with the atomizing air 46 with the flow rate increased through the grooves 81 (with the horizontal speed component increased) at the two-fluid converging space portion 43 and then sprayed from the spray hole 44. Compared to the case of not providing the two-fluid converging space portion 43 and grooves 81, the spread angle of the sprayed liquid fuel 24 is larger, and the liquid fuel 24 is surely atomized, thus improving the combustion characteristics of the liquid fuel 24.

Furthermore, the liquid fuel tank 19 is installed on the two-fluid spray nozzle 38 with the tapered surface portion (the outside portion 21 b-1 of the undersurface 21 b of the bottom portion 21) of the liquid fuel tank 19 abutted and fitted in the tapered surface portion (inner surface 38 a) of the two-fluid spray nozzle 38, and it is therefore easy to align the central axes of the liquid fuel tank 19 and two-fluid spray nozzle 38. Accordingly, the liquid fuel tank 19 is installed at the center. The width of the atomizing air passage 28 can be therefore made uniform in circumferential direction, so that the flow of the atomizing air 46 in the atomizing air passage 28 can be made uniform in the circumferential direction. It is therefore possible to secure the symmetric properties of the liquid fuel 24 (or symmetric properties of flame) sprayed from the spray hole 44 of the two-fluid spray nozzle 38.

Moreover, the grooves 81 of the bottom portion 21 of the liquid fuel tank 19 are formed along tangent directions of the circumference of the two-fluid converging space portion 43 in a top view. Accordingly, the atomizing air 46 is swirled and mixed with the liquid fuel 24 at the two-fluid converging space portion 43, and the liquid fuel 24 and atomizing air 46 are thus mixed more surely. The liquid fuel 24 sprayed from the spray hole 44 of the two-fluid spray nozzle 38 can be therefore surely atomized, thus improving the combustion characteristics of the liquid fuel 24.

Moreover, the plurality of grooves 81 of the bottom portion 21 of the liquid fuel tank 19 are formed at positions rotationally symmetric around the central axis of the two-fluid converging space portion 43. Accordingly, the liquid fuel 24 sprayed from the spray hole 44 of the two-fluid spray nozzle 38 can be uniformly distributed in the circumferential direction, thus improving the combustion characteristics of the liquid fuel 24.

In the two-fluid spray burner of Embodiment 4, by pressing the liquid fuel tank 19 downward by the coil spring 36 (see FIG. 4), the bottom portion 21 of the liquid fuel tank 19 is pressed against the two-fluid spray nozzle 38 to bring the tapered surface portion (outside portion 21 b-1) of the bottom portion 21 of the fuel tank 19 and the tapered surface portion (inner surface 38 a) of the two-fluid spray nozzle 38 into firm contact, thus preventing gap between these contact surfaces 21 b-1 and 38 a. It is therefore possible to prevent the atomizing air 46 from flowing into portions other than the grooves 81, thus allowing the effect of the wide spray by the grooves 81 to be sufficiently exerted.

Embodiment 6

FIG. 10( a) is a longitudinal sectional view showing a structure of lower part of a two-fluid sprayer in a two-fluid spray burner according to Embodiment 6; and FIG. 10( b) is a transverse sectional view taken along a line L-L of FIG. 10( a).

As shown in FIG. 10, in the two-fluid sprayer 12 of Embodiment 6, the inner surface (top surface) 21 a of the bottom portion 21 of the liquid fuel tank 19 is composed of a tapered (reverse conical) surface, and the fine liquid fuel discharge hole 22 is formed at the center (at the vertex position of the reverse conical tapered surface). The outer surface (undersurface) 21 b of the bottom portion 21 of the liquid fuel tank 19 is composed of a tapered (reverse truncated cone-shaped) surface. On the other hand, the two-fluid spray nozzle 38 does not include an atomizing air introduction portion (see FIG. 7) and is integrally formed with the sprayer outer cylinder 27 at the lower end of the sprayer outer cylinder 27 (a separate body may be fixed by welding or the like). In the two-fluid spray nozzle 38, the inner surface (top surface) 38 a is composed of a tapered (reverse conical) surface.

In the lower end portion of the outer peripheral surface 20 b of the side portion 20 of the liquid fuel tank 19, a plurality of supporting portions 91 are provided in a protruding manner (four in the example of the drawing). These supporting portions 91 are provided at equal intervals in the circumferential direction of the side portion 20. Outside portions 91 a-1 of undersurfaces 91 a are individually composed of tapered surfaces which are sloped inward along the inner surface 38 a of the two-fluid spray nozzle 38. The liquid fuel tank 19 is therefore supported with the outside portions 91 a-1 of the undersurfaces 91 a of the supporting portions 91 abutted and fitted to the inner surface 38 a of the two-fluid spray nozzle 38. Accordingly, the tapered (reverse truncated cone-shaped) gaps are secured between the outer surface 21 a of the bottom portion 21 of the liquid fuel tank 19 and the inner surface 38 a of the two-fluid spray nozzle 38 and serve as atomizing air passages 92. In other words, the first atomizing air passage 28 outside and the two-fluid converging space portion 43 inside communicate with each other through the second atomizing air passages 92.

The two-fluid converging space portion 43 is a reverse conical space formed in the central part of the two-fluid spray nozzle 38 by the inner surface 38 a of a tapered structure. The fine spray hole 44 is formed at the center of the two-fluid converging space portion 43 (the vertex position of the reverse conical space 43) and communicates with the two-fluid converging space portion 43. Specifically, the two-fluid converging space portion 43 is located under the liquid fuel discharge hole 22 and has a tapered structure including a circular plan view (top view) with the diameter thereof gradually reduced towards the spray hole 44.

After flowing down the atomizing air passage 28, the atomizing air 46 passes through atomizing air passage portions 93 between the supporting portions 91 and flows through the atomizing air passages 92 to be introduced to the two-fluid converging space portion 43. The atomizing air 46 collides and converges (is mixed) with the liquid fuel 24 discharged from the liquid fuel discharge hole 22 of the liquid fuel tank 19 at the two-fluid converging space portion 43. The liquid fuel 24 is atomized with the atomizing air 46 and then sprayed from the spray hole 44 of the two-fluid spray nozzle 38 together with the atomizing air 46 into the combustion space 13.

The configuration of the other parts of the two-fluid sprayer 12 of FIG. 10 is the same as that of the two-fluid sprayer 12 of FIG. 4. The configuration of the parts other than the two-fluid sprayer of the two-fluid spray burner of Embodiment 6 is the same as that of the two-fluid spray burner 11 of FIGS. 1 to 3.

According to the two-fluid spray burner of Embodiment 6, the following operational effects can be obtained, and in addition, the same operational effects as those of the aforementioned Embodiment 1 can be obtained.

Specifically, according to the two-fluid spray burner of Embodiment 6, the liquid fuel 24 which is discharged from the liquid fuel discharge hole 22 and flows into the two-fluid converging space portion 43 converges at the two-fluid converging space portion 43 with the atomizing air 46 which flows down the first atomizing gas passage 28, through the atomizing air passage portions 93 between the supporting portions 91, and through the second atomizing air passage 92 to be introduced into the two-fluid converging space portion 43 and is then sprayed from the spray hole 44 with the atomizing air 46. Accordingly, the liquid fuel 24 is mixed with the atomizing air 46 at the two-fluid converging space portion 43 and then sprayed from the spray hole 44 of the two-fluid spray nozzle 38. Accordingly, compared to the case of not providing the two-fluid converging space portion 43, the spread angle of the sprayed liquid fuel 24 is larger, and the liquid fuel 24 is surely atomized, thus improving the combustion characteristics of the liquid fuel 24.

Embodiment 7

FIG. 11 is a longitudinal sectional view showing a structure of a two-fluid spray burner according to Embodiment 7 of the present invention; and FIG. 12 is a transverse sectional view taken along a line M-M of FIG. 11.

As shown in FIGS. 11 and 12, in the two-fluid spray burner of Embodiment 7, the plate 18 is a porous plate. Specifically, in the ring-shaped plate 18, a plurality of combustion air holes 101 are formed. All of these combustion air holes 101 are provided inside of the combustion air hole 52 (first cylinder 16). Accordingly, after flowing down the combustion air passage 15, most of the combustion air 50 passes through the combustion air hole 52 on the outer periphery of the plate 19, flows through the combustion air passage 53 located outside of the first cylinder 16 and into the combustion space 13. Meanwhile, a part of the combustion air 50 flows through the combustion air holes 101 located inside of the first cylinder 16 and into the combustion space 13.

The configuration of the other parts of the two-fluid spray burner 11 of FIGS. 11 and 12 is the same as that of the two-fluid spray burner 11 of FIGS. 1 to 3.

According to the two-fluid spray burner of Embodiment 7, the following operational effects can be obtained, and in addition, the same operational effects as those of the aforementioned Embodiment 1 can be obtained.

Specifically, according to the two-fluid spray burner of Embodiment 7, by forming the plurality of additional combustion air holes 101 in the plate 18 position inside of the combustion air hole 52, a part of the combustion air 50 flows through these combustion air holes 101. Such a flow of the combustion air 50 can suppress stagnation of the combustion air occurring near the undersurface of the plate 18, thus reducing adherence of soot to the plate 18. Moreover, the cool combustion air flows near the two-fluid spray nozzle 38 through the other combustion air holes 101. It is therefore possible to obtain a cooling effect on the two-fluid spray nozzle 38, with the combustion air, which tends to be excessively heated by radiation heat from flame.

Embodiment 8

FIG. 13 is a system diagram schematically showing a fuel cell power generation system according to Embodiment 8 of the present invention. FIG. 13 shows an example of a case where the two-fluid spray burner of any one of the aforementioned Embodiments 1 to 7 is used as a heat source for a reformer in the fuel cell power generation system.

As shown in FIG. 13, a combustion furnace 112 is provided in upper part of a reformer 111, and the two-fluid spray burner 11 of any one of the aforementioned Embodiments 1 to 7 is inserted into the combustion furnace 112 from above. The two-fluid spray burner 11 is connected to a liquid fuel supply system, an atomizing air supply system, and a combustion air supply system which are not shown. The details of the two-fluid spray burner 11 are described above.

The reformer 111 is connected to an unillustrated raw material supply system. The raw material supply system supplies, to the reformer 111, water and reforming fuel which is raw material for reforming such as methane gas or kerosene. In the reformer 111, the reforming fuel is steam-reformed by using the large amount of combustion exhaust gas produced by combustion at the two-fluid spray burner 11, thus generating reforming gas (hydrogen rich gas).

The reforming gas generated by the reformer 11 is supplied to an anode side of a fuel cell 113 as fuel for power generation. In the fuel cell 113, the reforming gas (hydrogen) supplied to the anode side and air (oxygen) supplied to a cathode side are electrochemically reacted for power generation. The residual reforming gas not used in power generation at the fuel cell 113 is returned to the two-fluid spray burner 11 and used as gas fuel for burner combustion.

According to the fuel cell power generation system of Embodiment 8, the heat source of the reformer 111 is any one of the two-fluid spray burner 11 of the aforementioned Embodiments 1 to 7. Accordingly, the two-fluid spray burner 11 exerting the excellent effects as described above can provide, for the reformer 111, an improvement in performance, reduction of the costs and the like.

In the above description, the liquid fuel tank 19 includes only one liquid fuel discharge hole 22, but is not limited to this. The liquid fuel tank 19 may include a plurality of the liquid fuel tank 22.

In the above description, the liquid fuel discharge hole is provided in the bottom portion of the liquid fuel tank, but is not limited to this. The liquid fuel discharge hole may be provided in the side portion of the liquid fuel tank. Specifically, the liquid fuel tank may be of any type if the liquid fuel tank includes a cylindrical side portion and a bottom portion provided at the lower end of the side portion and is configured to store the liquid fuel supplied from the liquid fuel supply tube and discharge the stored liquid fuel through the single or the plurality of liquid fuel discharge holes which are opened below the liquid level of the stored liquid fuel and which are located in the side or bottom portion.

In the above description, the liquid fuel tank is provided within the sprayer outer cylinder, but is not limited to this. For example, it may be configured to provide the liquid fuel tank outside of the sprayer outer cylinder and supply the liquid fuel discharged from the liquid fuel discharge hole of the liquid fuel tank, through a tube or the like, to the space where the liquid fuel converges with the atomizing gas.

In the above description, the upper end of the liquid fuel tank is opened to allow pressure of the atomizing air flown into the atomizing air passage to act on the liquid level of the liquid fuel stored in the liquid fuel tank, but is not limited to this. It may be configured so that the upper end of the liquid fuel tank may be opened to the atmosphere, for example. In other words, the liquid fuel discharged from the liquid fuel supply tube is once stored in the liquid fuel tank, and produce a liquid column head of the liquid fuel by the pressure balance between the inside and outside (two-fluid converging space portion) of the liquid fuel tank. Thus, the stored liquid fuel is continuously discharged from the liquid fuel discharge hole.

Moreover, in the above description, two swirling-type grooves and four collision-type grooves are provided. But the numbers of grooves are not limited to these and may be set proper numbers. However, in order to secure a uniform spray of the atomized liquid fuel in circumferential direction, it is desirable that the number of grooves in swirling-type to be two or more and collision-type grooves to be three or more.

As described above, the configuration (invention) of providing the plate (shielding plate), first cylinder for delaying supply of combustion air, second cylinder for preventing stagnation and the like can be applied to not only the aforementioned two-fluid spray burner which includes a two-fluid sprayer, as a fuel spray, spraying liquid fuel and atomizing gas. It could also be applied to a burner including a fuel spray spraying only liquid fuel or a fuel spray spraying gas fuel.

Moreover, in the above description, the combustion air holes are provided on the outer periphery of the plate (shielding plate) by forming protrusions on the circumference of the plate (shielding plate) but is not limited to this. The combustion air holes only have to be provided on the outer periphery of the plate (shielding plate) and may be provided on the outer periphery of the plate by opening a hole in the periphery of the plate (shielding plate) itself, for example.

In the above description, the plate (shielding plate) is a horizontal plate but is not limited to this. The plate may be inclined obliquely downward from the inside towards the outside. For example, the plate 18 may be shaped in a truncated cone as virtually indicated by a dashed-dotted line in FIG. 11. Such an inclined plate can provide not only the function of keeping the combustion air away from the fuel spray nozzle (two-fluid spray nozzle 38) but also provide a function of delaying supply of combustion air, which is similar to the function of the first cylinder.

INDUSTRIAL AVAILABILITY

The present invention relates to a two-fluid spray burner which burns liquid fuel atomized with atomizing gas and is usefully applied to a two-fluid spray burner for a reformer of a fuel cell power generation system which may be operated in a condition where amount of liquid fuel supplied is small. 

1. A two-fluid spray burner which atomizes liquid fuel with atomizing gas and burns the atomized liquid fuel, the burner comprising: a liquid fuel tank including: a cylindrical side portion and a bottom portion provided at a lower end of the side portion, the liquid fuel tank storing liquid fuel supplied from a liquid fuel supply tube and discharging the stored liquid fuel from one or a plurality of liquid fuel discharge holes opened in the side or bottom portion at a position below a liquid level of the stored liquid fuel, the burner characterized in that the liquid fuel discharged from the liquid fuel discharge hole of the liquid fuel tank is atomized with the atomizing gas and burned.
 2. The two-fluid spray burner according to claim 1, characterized in that the liquid fuel discharge holes are opened in the bottom portion of the liquid fuel tank, the burner further comprising: a cylindrical atomizing gas passage formed between the side portion of the liquid fuel tank and an outer cylinder surrounding a periphery of the side portion; and a two-fluid spray nozzle provided at a lower end portion of the outer cylinder and including a lower nozzle main body and an upper atomizing gas introduction portion, the two-fluid spray nozzle having: a two-fluid converging space portion formed under the liquid fuel discharge holes, in central part of the nozzle main body and the atomizing gas introduction portion; one or a plurality of spray holes formed in the nozzle main body and leading to the two-fluid converging space portion; and one or a plurality of grooves formed in the atomizing gas introduction portion and allowing the two-fluid converging space portion and the atomizing gas passage to communicate with each other, the burner characterized in that the liquid fuel tank is installed on the atomizing gas introduction portion, and the liquid fuel which is discharged from the liquid fuel discharge holes to flow into the two-fluid converging space portion converges at the two-fluid converging space portion with the atomizing gas which flows down the atomizing gas passage and flows through the grooves at the atomizing gas introduction portion to be introduced to the two-fluid converging space portion, and the liquid fuel is then sprayed together with the atomizing gas from the spray holes.
 3. The two-fluid spray burner according to claim 2, further comprising an undersurface of the bottom portion of the liquid fuel tank formed as a tapered surface portion which is tapered, a top surface of the atomizing gas introduction portion also formed as a tapered surface portion which is tapered, and the liquid fuel tank installed on the atomizing gas introduction portion with the tapered surface portion of the liquid fuel tank abutted and fitted to the tapered surface portion of the atomizing gas introduction portion.
 4. The two-fluid spray burner according to claim 1, characterized in that the liquid fuel discharge holes are opened in the bottom portion of the liquid fuel tank, the burner further comprising: a cylindrical atomizing gas passage formed between the side portion of the liquid fuel tank and an outer cylinder surrounding a periphery of the side portion; and a two-fluid spray nozzle provided at a lower end portion of the outer cylinder, the two-fluid spray nozzle having: a two-fluid converging space portion formed in central part under the liquid fuel discharge holes, and one or a plurality of spray holes formed, leading to the two-fluid converging space portion, the burner characterized in that the undersurface of the bottom portion of the liquid fuel tank is formed as a tapered surface portion which is tapered, the top surface of the two-fluid spray nozzle is also formed as a tapered surface portion which is tapered, the liquid fuel tank is installed on the two-fluid spray nozzle with the tapered surface portion of the liquid fuel tank abutted and fitted to the tapered surface portion of the two-fluid spray nozzle, one or a plurality of grooves are formed at the bottom portion of the liquid fuel tank, the grooves allowing the atomizing gas passage and the two-fluid converging space portion to communicate with each other, and the liquid fuel discharged from the liquid fuel discharge holes to flow into the two-fluid converging space portion converges at the two-fluid converging space portion with the atomizing gas which flows down the atomizing gas passage and then flows through the grooves at the bottom portion of the liquid fuel tank to be introduced to the two-fluid converging space portion, and the liquid fuel is then sprayed together with the atomizing gas from the spray holes.
 5. The two-fluid spray burner according to claim 2, wherein the two-fluid converging space portion has a circular shape in a top view, and the grooves of the atomizing gas introduction portion or the grooves of the bottom portion of the liquid fuel tank are formed along tangent directions of a circumference of the two-fluid converging space portion in the top view.
 6. The two-fluid spray burner according to claim 2, wherein the two-fluid converging space portion has a circular shape in a top view, and the grooves of the atomizing gas introduction portion or the grooves of the bottom portion of the liquid fuel tank are formed along radial directions of the two-fluid converging space portion in the top view.
 7. The two-fluid spray burner according to claim 5, wherein the plurality of grooves of the atomizing gas introduction portion or the plurality of grooves of the bottom portion of the liquid fuel tank are formed at positions rotationally symmetric around a central axis of the two-fluid converging space portion.
 8. The two-fluid spray burner according to claim 2, further comprising: a press member pressing the liquid fuel tank downward, characterized in that the bottom portion of the liquid fuel tank is pressed against the atomizing air introduction portion of the two-fluid spray nozzle to be brought into firm contact or the bottom portion of the liquid fuel tank is pressed against the two-fluid spray nozzle to be brought into firm contact.
 9. The two-fluid spray burner according to claim 1, wherein the liquid fuel discharge holes are opened in the bottom portion of the liquid fuel tank, the burner characterized by further comprising: a cylindrical first atomizing gas passage formed between the side portion of the liquid fuel tank and an outer cylinder surrounding a periphery of the side portion; and a two-fluid spray nozzle provided at a lower end portion of the outer cylinder, the two-fluid spray nozzle having: a two-fluid converging space portion formed in center part under the liquid fuel discharge holes and one or a plurality of spray holes formed, leading to the two-fluid converging space portion, the burner characterized in that the top surface of the two-fluid spray nozzle is formed as a tapered surface portion which is tapered, the undersurface of the bottom portion of the liquid fuel tank is formed as a tapered surface portion which is tapered, a plurality of supporting portions protrude on the side portion of the liquid fuel tank, and each undersurface of the supporting portions is formed as a tapered surface portion, the liquid fuel tank is installed on the two-fluid spray nozzle with the tapered surface portions of the supporting portions being abutted and fitted to the tapered surface portion of the two-fluid spray nozzle, gap formed by the supporting portions between the tapered surface portion of the liquid fuel tank and the tapered surface portion of the two-fluid spray nozzle is a second atomizing gas passage, and the liquid fuel discharged from the liquid fuel discharge holes to flow into the two-fluid converging space portion converges at the two-fluid converging space with the atomizing gas which flows down the first atomizing gas passage, passes through atomizing gas passage portions between the supporting portions, and flows through the second atomizing gas passage to be introduced to the two-fluid converging space portion and is then sprayed together with the atomizing gas from the spray holes.
 10. The two-fluid spray burner according to claim 2, wherein the two-fluid converging space portion is a reverse conical shape, and the spray holes are formed at a vertex position of the reverse conical space.
 11. The two-fluid spray burner according to claim 2, further comprising a cylindrical gas fuel passage formed between the outer cylinder and a gas fuel supply tube surrounding a periphery of the outer cylinder, the burner characterized in that gas fuel flows down the gas fuel passage and is sprayed from a lower end of the gas fuel passage to be burned.
 12. The two-fluid spray burner according to claim 1, wherein an end of the liquid fuel supply tube is in contact with an inner peripheral surface of the side portion of the liquid fuel tank.
 13. The two-fluid spray burner according to claim 4, wherein the two-fluid converging space portion has a circular shape in a top view, and the grooves of the atomizing gas introduction portion or the grooves of the bottom portion of the liquid fuel tank are formed along tangent directions of a circumference of the two-fluid converging space portion in the top view.
 14. The two-fluid spray burner according to claim 4, wherein the two-fluid converging space portion has a circular shape in a top view, and the grooves of the atomizing gas introduction portion or the grooves of the bottom portion of the liquid fuel tank are formed along radial directions of the two-fluid converging space portion in the top view.
 15. The two-fluid spray burner according to claim 13, wherein the plurality of grooves of the atomizing gas introduction portion or the plurality of grooves of the bottom portion of the liquid fuel tank are formed at positions rotationally symmetric around a central axis of the two-fluid converging space portion.
 16. The two-fluid spray burner according to claim 6, wherein the plurality of grooves of the atomizing gas introduction portion or the plurality of grooves of the bottom portion of the liquid fuel tank are formed at positions rotationally symmetric around a central axis of the two-fluid converging space portion.
 17. The two-fluid spray burner according to claim 13, wherein the plurality of grooves of the atomizing gas introduction portion or the plurality of grooves of the bottom portion of the liquid fuel tank are formed at positions rotationally symmetric around a central axis of the two-fluid converging space portion.
 18. The two-fluid spray burner according to claim 4, further comprising: a press member pressing the liquid fuel tank downward, characterized in that the bottom portion of the liquid fuel tank is pressed against the atomizing air introduction portion of the two-fluid spray nozzle to be brought into firm contact or the bottom portion of the liquid fuel tank is pressed against the two-fluid spray nozzle to be brought into firm contact.
 19. The two-fluid spray burner according to claim 4, wherein the two-fluid converging space portion is a reverse conical shape, and the spray holes are formed at a vertex position of the reverse conical space.
 20. The two-fluid spray burner according to claim 9, wherein the two-fluid converging space portion is a reverse conical shape, and the spray holes are formed at a vertex position of the reverse conical space.
 21. The two-fluid spray burner according to claim 4, further comprising a cylindrical gas fuel passage formed between the outer cylinder and a gas fuel supply tube surrounding a periphery of the outer cylinder, the burner characterized in that gas fuel flows down the gas fuel passage and is sprayed from a lower end of the gas fuel passage to be burned.
 22. The two-fluid spray burner according to claim 9, further comprising a cylindrical gas fuel passage formed between the outer cylinder and a gas fuel supply tube surrounding a periphery of the outer cylinder, the burner characterized in that gas fuel flows down the gas fuel passage and is sprayed from a lower end of the gas fuel passage to be burned. 